Marijuana: THC and Analogsby Michael Valentine Smith
Cannabis sativa has been a cherished friend of an ever-increasing proportion of mankind since prehistoric times. The genus Cannabis contains only this one species, but its appearance and psychedelic properties vary tremendously depending on growth conditions. It seems to have originated in Asia, but its "medicinal" properties and the long fibers in its stem used to make rope (hemp) have led to its being carried all over the world. The early American colonists brought seeds with them and George Washington, "the father of our country," was among its cultivators. There is evidence for Cannabis use as early as 5,000 B.C. in Central Europe and there are probable references to it in the earliest writings of China and Egypt. The frozen tombs of the inhabitants of Siberia in about 500 B.C. have yielded quantities of seeds along with a variety of devices for burning them. A very hot, dry climate appears necessary for producing grass with high psychedelic activity, which may account for the failure to use Cannabis as an intoxicant in Northwestern Europe.
Grass seems to grow best in loose, well fertilized soil (manure, superphosphates). The soil should be well tilled, and the seeds (actually drupes or achenes, a type of nut) sown about one inch apart in rows about one foot apart and covered with about 3/4 inch of soil. Some say it is best to use dark (not green) seeds, and to soak them overnight in water before sowing. They can be sown in flatboxes and transplanted when about two to six inches high (about two weeks). After the plants have their first two leaves they can be thinned by pulling up those which look the weakest. Cannabis is usually dioecious (male and female flowers on separate plants). The female plants are widely believed to contain more THC than the males, but this varies from strain to strain. In India, the males are apparently weeded out before they have a chance to pollinate the females and initiate seed development in the belief that the unfertilized females produce stronger grass. This is unproven, and even if true, the total yield of THC from a field of males plus fertilized females may well be greater. The males are generally taller and thinner until almost mature (3 - 4 months), when the females may become taller. Males tend to yellow and die some weeks before the females. Harvest takes place around September in Europe and Japan and around July in North Africa. The sex of the plants can be influenced by soil conditions, some experiments giving more males in moist, heavily manured soils. Long light periods tend to masculinize, whereas plants grown under short day conditions (for example, those seeded in northern latitudes in winter) tend to produce intersexual flowers, males changing to females; a condition also resulting from debudding males. It has recently been found that male flowers tend to change to females after early spraying with Ethrel (2-chloro-ethane-phosphonic acid). Under some conditions, flowering may occur in as little as two weeks. A sizable portion of the leaves can be harvested after about two months and the plants will continue to grow. The effects of these various manipulations on the THC yield of a single plant, or the crop as a whole, have yet to be determined. "The Induction of Flowering," L. Evans (ed.), 205(1969) is a good reference on Cannabis flowering. Pinching off the shoot tip when the plants are just beyond the seedling stage, and pinching off subsequently developing side shoots at about weekly intervals thereafter in order to keep the plant only a few feet tall, can produce plants so altered in shape, color and leaf morphology as to be unrecognizable as cannabis. The resins are said to accumulate on the surface of such distorted plants to such an extent that it looks crystalline, and the resulting grass is supposed to be as strong as hashish. For definitive references on the cultivation and chemistry of marijuana, see MARIJUANA GROWERS GUIDE, And/Or Press (1978) and MARIJUANA POTENCY, And/Or Press (1977).
Some samples of grass have considerable THC acid. In order to extract this it is first necessary to decarboxylate it by heating it to 110ø for fifteen minutes. Grass grown commercially for its fiber content, as well as that grown in northern Europe or much of the U.S.A., contains mostly the inactive cannabidiol and cannabidiolic acid. These compounds can be extracted and used to synthesize the active THC and THC acid (by smoking, not active orally) in one step. See TET 21,1228(1965) or the following. To extract, add 50g grass/liter petroleum ether or benzene; soak twelve hours with occasional shaking; filter and extract petroleum ether three times with a solution containing 5% NaOH and 5% Na2SO3. Acidify the aqueous extracts with cold dilute sulfuric acid and extract with ether or chloroform which is dried, evaporated in a vacuum to yield the cannabidiolic acid. THC and cannabidiol remain in the petroleum ether which can be dried and evaporated in a vacuum and the residue added to grass. THC acid is converted to THC by boiling in benzene for seven hours.
THC Extraction for Smuggling or Converting Poor Grass to Good
This is recommended to anyone who wants to smuggle or otherwise conceal grass or hash. One hundred kilos of grass will convert to about two or three kilos of resin, which can later be redissolved and absorbed on alfalfa, etc. See Lloydia 33,453(1970) for a method of large scale extraction. Cover grass or hash with methanol, benzene, petroleum ether, or isopropyl (rubbing) alcohol. Allow to soak for about twelve hours, filter and repeat soaking with fresh solvent. This process can be speeded up by gently heating the solvent plus grass (no flames) for about three hours, adding more solvent if necessary. Evaporate the combined solvent extracts until a resin is obtained or until syrupy and absorb the syrup on grass, etc. Repeat the process until no more resin is obtained, or until smoking some of the residual grass indicates that all the THC has been extracted. Methylene chloride works very well. Unleaded gas, preferably without additives (white gas), paint thinner or remover, or turpentine should be satisfactory. For a detailed discussion, see MARIJUANA POTENCY, And/Or Press (1977).
Smoking seems to destroy most of the THC, but even so, this is several times more efficient than eating it, since the smoking dose of delta-1 THC is about 2mg and the eating dose about 10mg. Based on a 5% THC content, 1g of hash efficiently used should (by smoking) stone about 25 people. Partial tolerance to THC develops rapidly and most users observe that they get much higher the first time a given batch of grass is smoked than on subsequent occasions. However, for unknown reasons, tolerance to grass of different origin seems less, leading some people to desire a different batch for each day of the week.
Official THC Tests
One-tenth gram powdered grass, 5ml petroleum ether; grind in mortar and let soak fifteen minutes. Filter and add 1ml of the petroleum ether carefully to 2 ml 15% HCl in absolute ethanol. Red color at boundary of two layers indicates THC. After shaking, the upper layer is colorless and the lower orange-pink which turns colorless after addition of 1 ml of water. Alternatively, evaporate the petroleum ether, add 2 ml Duquenois reagent ( 12 drops acetaldehyde, 1 g vanillin, 50 ml ethanol), 2 ml HCl and stir. Let stand 10 minutes and add 2 ml chloroform; shake and let separate. A purple chloroform layer indicates THC. Also useful but less specific is the fact that THC gives a purple color with 5% KOH in ethanol. A few grains of sucrose will often intensify color development in these tests. (See Bulletin on Narcotics 22,33(1970)).
Is It Legal?
The delta-1 and delta-1(6) THC's with the n-pentyl in the 5' position (obtained by using olivetol in the syntheses) are naturally occurring and hence illegal, but the delta-3 THC's and the numerous isomers, homologs and analogs of the delta-1 and delta-1(6) compounds are probably legal. Apparently, recent federal legislation outlaws delta-1, delta-1(6), delta-3,4-THC's, both cis and trans and D and L and compounds. This still leaves hundreds of legal cannabinoids.
THC refers to tetrahydrocannabinol, and delta refers to the position of the double bond. Various numbering systems are used, so the following equivalences should be noted: delta-1-THC = delta-1-3,4-trans-THC = delta-9-THC and delta-6-THC = delta-1(6)-THC = delta-8-THC = delta-6- 3,4- trans-THC. Little careful human testing has been done, so data given here and elsewhere on the relative psychedelic activity of various cannabinoids is often only a rough guess. Delta-1-THC and delta-6-THC have about the same activity which is about five times that of delta-3- THC. Cannabidiol, cannabidiolic acid, cannabinol, cannabigerol and cannabichromene all have very little or no activity. Only the L (-) isomer of THC seems to be active. When the n-pentyl at the 5' position is replaced by 1,2-dimethylheptyl, potency and duration of action increases about five times, giving the most active THC analog yet tested. It should be noted that recent testing has indicated that a 1,1- dimethylheptyl or 1-methyloctyl and probably similar side chains give THC's of equal or greater activity than the 1,2-dimethylheptyl cpd. However, the difficulty of synthesizing these compounds plus their very long action (up to several days or more) makes it doubtful whether they deserve all the interest they have generated among psychedelic enthusiasts. More concern should be devoted to the shorter side chains, since they would presumably allow one to get very stoned but to be straight again within a few hours, thus allowing the drug to be more easily manipulated. Substituting N, O, or S atoms at various places or saturating the double bond to produce hexahydrocannabinol probably retains activity. (See CA 74,125667(1971) for S analogs.) Alkoxy side chains at 5' retain activity. Unsaturated side chains are as active as saturated ones. Ether moieties at the 5' position, but not at the 3', retain activity. Activity is retained if an additional alkyl is placed at 4' but lost if placed at 6'. Activity is greatly decreased or lost if the H at the 4' or 6' positions is replaced by carboxyl, carbomethoxyl, acetyl or acetoxyl; if the hydroxyl is replaced by H; if the OH is at 5' and the side chain at 4'. Methyl and/or ethyl at 1 and 5 retains activity, as does removal of the methyl at 1. An hydroxyl in the side chain is active, but not on the first carbon of the side chain. Esterifying the OH retains activity, but etherifying eliminates activity. THC can be synthesized via cannabigerol and cannabichromene in low yield (TET 24,4830(1968), TL 5349,5353(1969), Proc. Chem. Soc. 82,(1964)). For several moderately difficult routes leading to delta- 1(6)-THC via cannabinol in about 10% yield, see LAC 685,126( 1965). For a synthesis of delta-1(6)-THC from cinnamyl derivatives and isoprene see JACS 89,4551(1967). A rather difficult synthesis of delta-1 and delta- 1(6)-THC is given in JACS 89,5934(1967). For a variety of THC analogs of unknown activity see BSC 1374, 1384(1968); JCS 952(1949); JACS 63,1971, 1977,2766(1941), 64,694,2031,2653(1942), 67,1534(1945), 70,662( 1948), 71,1624(1949), 82,5198( 1960); CA 75,48910 (1971); TL 3405(1967); JMC 11,377(1968); CT 2,167(1967); CA 76,126783(1972). Since 0 or 1 and perhaps 2 double bonds anywhere in the lefthand ring below, as well as changes in the size and position of the alkyl groups will probably all produce compounds with THC activity, many compounds similar to menthadieneol, menthatriene, verbenol, epoxycarene, pulegone and 4- carbethoxy-1-Me-3-cyclohexanone can be used in the methods below to get active THC analogs (e.g., isopipertinol will work (TL 945 (1972))). Also, 5-chlororesorcinol and 5-methylresorcinol (orcinol) have been shown to give weakly active THC's (see CA 76,33946(1972), US Patent 3,028,410 (1962), and TET 23,3435(1967) for syntheses of orcinol and related compounds). Unfortunately, recent data indicate that orcinol gives a THC with very low activity. It appears that delta-5 and delta-7 THC have very little activity. If the methyl groups at carbon 8 in THC are changed to longer alkyl groups, the activity decreases, but the replacement of the alkyl groups by hydrogen or other groups has not been carried out. Open chain analogs also have activity (see CT 2,167( 1967)). For new information on the structure-activity relationships of cannabinoids see JMC 16, I 200( 1973), Arzneim, Forsch 22,1995 (1972), and Chem. Revs. 76,75(1976). For THC analogs see JMC 19,445-71,549- 53(1976); Eur. JMC 10,79(1975); Phytochem.14,213(1975); CA 82,57564,170672-3(1975); Diss. Abst. 34B,1442(1973); J. Labelled Cpds. 11,551 (1975); Compt. Rend. Acad. Sci. 281C,197(1975). For THC in one step from chrysanthenol see Experientia 31,16(1975).
The following gives the synthesis of a water soluble THC derivative which is equipotent with THC and perhaps more rapidly acting (see Science 177,442(1972)). Stir equimolar amounts of THC, dicyclohexylcarbodiimide and gamma-morpholinobutyric acid hydrochloride (or gamma-piperidinobutyric acid hydrochloride) (JACS 83,2891 ( 1961 )) in methylene chloride at room temperature for 16 hours and filter, evaporate in vacuum (can triturate with ether and filter). The cost of synthetic THC will vary greatly depending on many factors, but high quality grass can probably be produced for under $20 a kilo. For good reviews of marijuana chemistry see Prog. Chem. Natural Prod. 25,175( 1967), Science 168,1159(1970), C. Joyce and J. Curry (Eds.), Botany and Chemistry of Cannabis ( 1970), JACS 93,217( 1971 ), JPS 60,1433( 1971 ), Ann. N.Y. Acad. Sci. 191(1971), Prog. Org. Chem. 8,78(1973), Marijuana- R. Mechoulam (Ed.) (1973), and Chemical Reviews 76,75(1976). Only the first three methods below give the natural L (-) isomer of THC. The other methods give the racemic produce and consequently their yields of active THC are actually one-half that indicated.
Syntheses of THC and Analogs
L-(-)-delta-1(6)-THC HCA 52,1123(1969), cf. JACS 96,5860(1974).
This method gives about 50% yield for THC and about 90% for the 1',1'- dimethylpentyl analog. Olivetol 4.74 g (or equimolar amount of analog), 4.03 g (+) cis or trans p-methadien (2,8)-ol-1 (the racemic compound can be used but yield will be one-half), 0.8 g p-toluenesulfonic acid in 250 ml benzene; reflux two hours (or use 0.004 Moles trifluoracetic acid and reflux five hours). Cool, add ether, wash with NaHCO3 and dry, evaporate in vacuum to get about 9 g of mixture (can chromatograph on 350 g silica gel - benzene elutes the THC; benzene:ether 98:2 elutes an inactive product; then benzene:ether 1:1 elutes unreacted olivetol; evaporate in vacuum to recover olivetol).
Dissolve the olivetol or analog and p-menthadienol or p-methatriene (1,5,8) in 8 ml liquid SO2 in a bomb and fuse 70 hours at room temperature. Proceed as above to get about 20% yield. L (-)-delta-1(6)- THC JACS 89,4552(1967), JCS (C) 579(1971), cf. Diss. Abst. 35B,3843(1974), and Phytochemistry 14,213 (1975). Convert (-) alpha- pinene to (-) verbenol (see precursors section). Add 1M(-) verbenol (racemic verbenol will give one-half yield), 1M olivetol or analog with methylene chloride as solvent. Add BF3 etherate and let stand at room temperature one-half hour to get approximately 35% yield after evaporating in vacuum or purifying as above to recover unreacted olivetol. Solvent and catalyst used in Method 1 above will probably also work. Either cis or trans verbenol can be used. The JCS paper adds 1 g BF3-etherate to a solution of 1 g olivetol and 1.1 g verbenol in 200 ml methylene chloride and let stand two hours at room temperature. JACS 94,6164(1972) recommends two hours at -10øC, then one-half hour at room temperature and the use of cis rather than trans verbenol (the latter gradually decomposes at room temperature). The reaction is also carried out under nitrogen, using twice as much verbenol as olivetol, 0.85 ml BF3 etherate and 85 ml methylene chloride/g verbenol (both freshly distilled over calcium hydride) to give ca. 50% yield. See also JACS 94,6159(1972) for the use of citral and Arzneim. Forsch. 22,1995(1972) for use of p-TSA. In the synthesis of THC with verbenol, the cis isomer is preferable to the trans since the latter decomposes at room temperature. Pinene or cawone give active THC's (JMC 17,287(74)).
L(-)-delta-1 and delta-1(6) THC JACS 92,6061(1970), U.S. Patent 3,734,930. 1M (+)-trans-2-carene oxide (2-epoxycarene), 1M olivetol or analog, 0.05 M p-toluenesulfonic acid in 10L benzene; reflux two hours and evaporate in vacuum (or can separate the unreacted olivetol as above) to get about 30% yield THC. Olivetol can also be separated as described below. For synthesis of 2-epoxycarene (delta-4 carene oxide) from delta-4 carene (preparation given later) see p-methadieneol preparation (Method 2). 3-carene oxide gives 20% yield of delta-1(6) THC.
Methods for Racemic THCDelta-3 THC JACS 63,2211 (1941)
1M pulegone, 1M olivetol or analog, 0.3 M POCl3, reflux four hours in 1 L benzene and evaporate in vacuum or pour into excess saturated NaHCO3 and extract with dilute NaOH to recover unreacted olivetol. Dry, and evaporate in vacuum the benzene layer to get the THC.Delta-1(6) THC from Cannabidiol HCA 52,1123(1969)
Reflux 1g cannabidiol, 60 mg p-toluenesulfonic acid (or 0.003 M trifluoroacetic acid) in 50 ml benzene for 1 1/2 hours. Evaporate in vacuum to get about 0.7 g THC. Alternatively, add 1.8g cannabidiol to 100 ml 0.005N HCl and reflux four hours. Proceed as above to get about 0.5 g THC (cf. JACS 94,6159 (1972)).Nitrogen Analogs of Delta-3 THC CA 72,66922(1970); JACS 88,3664(1966), TL 545(1972)
5.4 g olivetol or 0.03M analog, 5.8 g 4-carbethoxy-N-benzyl-3- piperidone hydrochloride or 0.03M analog (JACS 71,896(1949) and 55,1239(1933) give an old and clumsy synthesis, and Heterocyclic Compounds, Klingenberg (Ed.), part 3, chaps. IX-XII (1962) gives information on related compounds) in 10 ml concentrated sulfuric acid. The concentrated sulfuric acid should be added dropwise, with cooling (cf. U.S. Patent 3,429,889). Add 3 ml POCl3 and stir at room temperature for 24 hours. Neutralize with NaHCO3 to precipitate 2.3g (I). Filter; wash precipitate with NaHCO3 and recrystallize from acetonitrile. Dissolve 4.3 g (I) in 30 ml anisole and add 0.1 M methyl MgI in 50 ml anisole. Stir 12 hours and evaporate in vacuum or acidify with sulfuric acid, neutralize with NaHCO3 and filter; wash to get 2.4 g N-benzyl analog of THC. For other N-analogs of unknown activity see JOC 33,2995(1968). Recover unreacted olivetol as usual.
The 5-aza analogs given in the JOC ref. seem to be active but they use the pyrone intermediate from certain routes of THC synthesis for a precursor. See U.S. Patent 3,493,579 (03 Feb 1970) for quinuclidine analogs and JOC 38,440(1973) for a different approach to N-analogs. See JOC 39,1546(1974) and HCA 56,519(1973) for other N-analogs.Delta-1(6) THC U.S. Patent 3,576,887
This synthetic route allows one to proceed from the alkylresorcinol dimethyl ether without using a compound of the verbenol or cyclohexanone type. Synthesis of olivetol aldehyde (Aust. J. Chem. 21,2979 (1968)). To a stirred solution of phenyllithium (1.6g bromobenzene and 0.16g Li) in 50 ml ether, add 0.01M olivetol dimethyl ether (or analog -- see elsewhere here for preparation) in 5 ml ether and reflux 4 hours. Add 5 ml N-methylformanilide, reflux 1 hour and wash with 2x50 ml dilute sulfuric acid, 50 ml water, 25 ml saturated NaCl and dry, evaporate in vacuum the ether (can dissolve in benzene and filter through 100g of alumina) to get 60% yield of the dimethylolivetol aldehyde (I) (recrystallize from ether-pentane). Can recover unreacted starting material by refluxing the vacuum distillate 3 hours with excess 10% HCl, removing the organic layer and extracting the aqueous layer with ether: wash and dry, evaporate in vacuum the combined ether layers. An alternative method for (I) (JACS 65,361(1943)). In a 200 ml 3 neck round bottom flask with a stirrer, a reflux condenser, a dropping funnel and a nitrogen inlet tube, introduce a rapid stream of nitrogen and in the stream issuing from the central neck, cut 1.5g of lithium into ca. 70 pieces and drop into the flask containing about 25 ml dry ether. Place the fittings in position, slow the nitrogen stream and add 1/2 of the solution of 9.2g n-butyl-chloride in 25 ml dry ether. Start the stirring and add the rest of the n-butyl-chloride at a rate giving a gentle reflux. Continue stirring and reflux 2 hours and add 15 ml olivetol dimethyl ether in 25 ml dry ether. Reflux 2 hours and add dropwise a solution of 15 ml N-methylformanilide in 25 ml dry ether with stirring at a rate sufficient to produce refluxing. Continue stirring 1 hour, treat with 3% sulfuric acid and then pour into excess of this acid. Remove upper layer and extract aqueous layer twice with ether. Wash combined ether layers with dilute aqueous NaHCO3 and water and dry, evaporate in vacuum the ether (can distill 148-52/0.3) to get 78% (I). JACS 65,361(1943). A mixture of 6.5g (I) (or analog), 20 ml pyridine, 1 ml piperidine and 9g malonic acid is warmed on a steam bath 1 hour. Add another 1 g malonic acid and heat another 1/2 hour. Reflux 1/2 hour and pour into excess iced 10% HCl, stirring occasionally over 2 hours. Filter and dry to get 6 g 2,6-dimethoxy-4-n-amycinnamic acid (II) (recrystallize from ethanol). 10g (II), 40 ml 80% isoprene and 40 ml dry xylene or toluene is heated in an autoclave at 185øC for 15 hours. Cool, dilute with 160 ml petroleum ether and shake with 100 ml saturated aq. Na2CO3. Let stand and separate the middle layer. Wash the middle layer with a mixture of petroleum ether and dilute aq. Na2CO3 and again separate the middle layer and treat with 75 ml 10% HCl and 75 ml ether. Shake, separate the aqueous layer and wash the ether 3 times with water. Dry and evaporate in vacuum the ether and dissolve the residue in petroleum ether. The solid which ppts. after about 10 minutes is unchanged (II). Filter and let stand in refrigerator overnight and dry and evaporate in vacuum to precipitate about 7 g of the 1-methyl-5 (2,6- dimethoxy-4-n-amylphenyl)-1-cyclohexene-4-COOH (III) (recrystallize from petroleum ether). 1g (III) in 5 ml dry ether is added to 10 ml 3M MeMgI (from 0.21 g Mg and 1.2g methyl iodide) in ether, heated to 130øC to evaporate the solvent and the oil kept at a bath temperature of 165ø C for 1/2 hour. Cool in dry ice-acetone bath and cautiously add ammonium chloride-ice water mix to decompose the excess Grignard reagent. Acidify with dilute HCl and extract with ether. Wash with NaCl, dilute K2CO3, NaCl and dry, evaporate in vacuum to get the dimethyl derivative (IV). Reflux (IV) in 25 ml benzene with 100 mg p-toluenesulfonic acid for 1 hour with a Dean-Stark trap and dry, evaporate in vacuum (or wash with NaHCO3, NaCl first) to get the THC or analog. Hydrolysis of benzopyrones (for synthesis see elsewhere here) will produce compounds of type (III) which will work in this synthesis. The hydrolysis proceeds as follows (JCS 926(1927)): Add 10g of the benzopyrone to 20g 30% NaOH, cool and shake 1 hour with 19 ml methylsulfate. Extract the oil with ether and dry, evaporate in vacuum to get the ester. Acidify the aqueous solution and filter, wash, dissolve ppt. in sodium carbonate and acidify, filter to get the free acid. Both the acid and the ester will work in this synthesis. For a possible route to benzopyrones via condensation of isoprene and 3-CN-5-OH-7-alkyl-coumarin see JACS 82,5198( 1960). See JMC 16,1200 (1973) for another ref. on the pyrone route to THC.Delta-3 THC Analogs TET 23,77(1967)
11.6g 5-(1,2-dimethy))-heptyl resorcinol or equimolar amount of olivetol or other analog, 9.2g 2-carbethoxy-5-methyl cyclohexanone (4-carbethoxy- 1-methyl-3-cyclohexanone), 5 g POCl3, 70 ml dry benzene (protect from moisture with CaCl2 tube). Boil 5 minutes (HCl evolution) and let stand at room temperature 20 hours. Pour into 10% NaHCO3, separate the benzene layer and wash with 3x50 ml 10% NaHCO3. Dry and evaporate in vacuum the benzene and recrystallize from 50 ml ethyl acetate to get 6.6 g of the pyrone (I). 4.5g (I), 150 ml benzene; add dropwise to a solution prepared from 7.8 g Mg, 18 ml methyl iodide, and 90 ml ether. Reflux 20 hours and add 45 ml saturated NH4Cl. Separate the organic layer and extract the aqueous phase with benzene. Combine the organic layer and benzene and dry, evaporate in vacuum to get the THC analog.Delta-3 THC analogs from Resorcinol TET 23,83(1967)
22g resorcinol,36 g 4-carbethoxy-1-methyl-3-cyclohexanone, 20g polyphosphoric acid; heat to 105øC and when the exothermic reaction which occurs subsides, heat at 140øC for one-half hour. Pour onto ice- water; filter; wash with water and recrystallize-ethanol to get 34g of the pyrone (I). 6.4g (I), 8 ml caproyl-Cl or analog (for preparation see above reference, page 84); heat on oil bath (can use mineral oil) at 120øC until the exothermic reaction subsides (HCl evolution). Cool and pour into ethanol. Filter to get 8g precipitate (II). 3.2g (II), 4.4g dry AlCl3; heat on oil bath at 170øC for one hour. Cool and add HCl; filter and dissolve precipitate in 7 ml 2N NaOH. Filter and acidify with HCl to precipitate 1.4 g (III) (recrystallize-ethanol). Test this for activity. Use benzoyl-Cl or benzoic anhydride to esterify the OH group (this may not be necessary), methyl MgBr or methyl MgI to methylate the keto group, and sulfuric acid to dehydrate and hydrogenate as described elsewhere here to get the THC analog. Since the resulting THC analog has the side chain at the 6' position, it may not be active. This paper also gives a synthesis for THC analogs with the side chain in the 4' position, but again their activity in man is unknown. Verbenol, etc., should work in this synthesis, thus obviating the need for the methylation step.Delta-1(6) THC JACS 88,367(1966)
1 M olivetol or analog, 1 M citral in 10% BF3 etherate in benzene about eight hours at 5-10øC. Extract unreacted olivetol with dilute NaOH and evaporate in vacuum the ether to get about 20% yield of the trans THC, and 20% of the cis THC which can be converted to the active trans isomer by reacting with BBr3 in methylene chloride at -20øC for 1 1/2 hours. (TL 4947(1969)). Alternatively, the reaction can be carried out in 1 % BF3 etherate in methylene chloride to get 20% Delta-1 THC.Delta-3 THC Analogs JACS 63,1971(1941) cf. CA 82,170672-3 (1975)
7.6g 5-n-heptyl resorcinol or equimolar amount analog, 6.6g (0.037M) 4- carbethoxy-1-methyl-3-cyclohexanone or analog, 5.8g POCl3 in 60 ml benzene. Reflux 5 hours, cool and pour into NaHCO3 to get about 6 g THC analog and 1 g more by concentrating the mother liquor, or proceed as described elsewhere here to recover unreacted resorcinol. 3-carbethoxy- 1-methyl-2 or 4-cyclohexanone, 2-carbethoxy-cyclohexanone, etc. will probably also give active THC analogs.Delta-3 THC Analogs JCS 952(1949)
1.75 g 2-Br-4-methyl-benzoic acid, 1.5 g olivetol or analog, 10 ml 1N Na OH and heat to boiling; add 0.5ml CuSO4. Filter; wash with ethanol and recrystallize from ethanol to get (I). 10g (I) in 150 ml benzene; add to methyl-MgI prepared from 47.5 g methyl iodide, 8 g Mg, 120 ml ether. Reflux fifteen hours, cool and pour on ice. Add saturated NH4Cl and separate the ether. Wash two times with water and dry and evaporate in vacuum the ether to get the THC.
Precursors For THC Synthesis
p-Menthatriene (1,5,8) BER 89,2493(1956)
90g d(+) carvone (l(-) carvone or racemic carvone probably will work also) in 150 ml ether; add dropwise with stirring to 7.5 g lithium aluminum hydride in ether. Heat one hour on water bath; cool and carefully add water and then ice cold dilute sulfuric acid. Separate the ether and extract the aqueous layer with ether; dry and evaporate in vacuum the combined ether to get about 60 g product (can distill 65/14).
(+) Cis and Trans p-Menthadien-(2,8)-OL-1
LAC 674,93( 1964) cf. BSC 3961(1971), JOC 38,1684(1973)
136g (+)limonene in 2 liters methanol; 2g bengal rose dye. Illuminate with a high voltage Hg lamp (e.g., HgH 5000) for fourteen hours or until about 1M of O2 is taken up. Evaporate the methanol at 0-10øC to about 500 ml and then stir with ice cooling and add this solution dropwise to solution of 250 g Na2SO3 in 1.5 liters water and continue stirring for twelve hours. Heat two hours at 70øC and extract with ether and dry, evaporate in vacuum (can distill with addition of Na2CO3 at 40-70/0.2) to get about 100 g mixture containing about 40% product which can be purified by fractional distillation.
HCA 48,1665(1965) Convert (+) Delta-3 carene to (+) trans-4- acetoxycarane (I) via (+) trans-4-OH-carane. Reflux 50 g (I) for 45 minutes (180øC oil bath under N2 or Argon). Cool and can distill (57/10) to get about 25 g mixture of Delta-3 and Delta-4 carene (residue is unchanged starting material) containing about 60% Delta-4 isomer. Alternatively, to 150 ml ethylene diamine add portionwise with stirring at 110øC under Argon or N2, 5.3 g Li metal; after one hour add dropwise 110g (+) Delta-3 carene. After one hour cool to 4øC and add water. Extract with ether, wash the ether five times with water and dry, evaporate in vacuum to get 100 g of a mix containing about 40% (+) Delta-4 carene (can separate by fractional distillation). Delta-4 carene can also be obtained from Delta-3 carene as follows: (JCS(C)46(1966)): Dissolve 1 g Delta-3 carene in 50 ml propionic acid and heat at a suitable temperature (e.g., one- half hour at room temperature may do) in presence of 1/2g Palladium-Carbon catalyst (5%) in ethanol and filter, evaporate in vacuum (can distill 63.5/19.5). See J.Soc. Cosmet. Chem. 22,249(1971) for a review of (+) Delta-3 carene chemistry.
Delta-2 Carene oxide (2-epoxycarene) LAC 687,22(1965), (cf. TL2335(1966), and CA 68:22063(1968))
To 136 g 04 carene in 330 ml methylene chloride and 120 g anhydrous sodium acetate, add dropwise with vigorous stirring in an ice bath, 167 g of 50% peracetic acid and continue stirring for ten hours. Heat to boiling for two hours, cool, wash with water, sodium carbonate, water, and dry, evaporate in vacuum the methylene chloride to get about 100 g p-menthadieneol. Apparently (CA 68,22063(1968)) substituting sodium carbonate for sodium acetate results in the production of Delta-2 carene oxide (2-epoxycarene) in about 50% yield (can distill 63/7).
4-Carbethoxy-1-methyl-cyclohexanone LAC 630,78(1960)
Cool 20 g of sodium metal in 325 ml ethanol to -15øC in an ice-salt bath and add in small amounts over one hour a solution of 100 g 3-methyl- cyclohexanone and 150 g diethyloxalate (keep temperature below -10øC). Keep three hours in cold and then twelve hours at room temperature. Add solution of 1.3 L of water, 60 ml 2N sulfuric acid. Separate the yellow- brown oil and extract the water with ether or CHCl3 until the yellow is removed. Combine the oil and the extract and distill the solvent and the unchanged starting material (100øC bath, 13 mm). Slowly heat the residue in a one-half liter flask with air cooling. CO2 evolution starts at 160øC. Continue heating to 220øC and keep at this temperature for 1 1/2 hours or until a test with 1% ethanol-FeCl3 solution shows the end of the reaction by a violet color (unconverted material gives a brown color). Can distill two times in Vigreux column to give about 83 g of oily colorless product.
(-)Verbenol JCS 2232(1961)
Racemic alpha-pinene will yield racemic verbenol which will give one- half the yield of (-)verbenol.
27 g (-)alpha-pinene in 500 ml dry benzene; heat and keep temperature at 60-65øC throughout. Add with stirring over 20 minutes 84 g dry (dry over P2O5) lead tetra-acetate. Stir one-half hour; cool and filter and add filtrate to water. Filter and evaporate in vacuum the benzene layer (can distill 96-7/9) to get 21.2 g cis-2-acetoxy-pin-3-ene(I). 5 g (I) in 25 ml glacial acetic acid; keep at 20øC for one-half hour and add water and extract with ether. Wash the extract with aqueous Na2CO3 and evaporate in vacuum the ether (can distill 97-8/9) to get 4.3 g trans verbenyl acetate (II). Hydrolyze (II) with NaOH to give the (-) cis and trans verbenol. For other methods of producing verbenol see CA 37,361(1943), CA 57,16772(1962) and BSC 2184(1964), JCS (B) 1259(1967). The last paper also gives a method for converting (-) beta-pinene to (-) alpha-pinene. See also CA 65,2312(66). 5-Alkyl Resorcinols from Acyl Resorcinols CA 72,66922(1970)
Compounds I-III may be able to give active THC analogs if used in place of olivetol for synthesis.
45 g 1-(3,5-dimethoxyphenyl)-1-hexanone(I) or analog (for preparation see the following methods) in 400 ml ether and 0.3 M methyl-MgI in 150 ml ether react to give 49 g 2-(3,5-dimethoxyphenyl)-2-heptanol(II). Heat 49 g (II) with 1 ml 20% sulfuric acid to 105-125øC/30mm for 1 1/2 hours to get 34 g of the 2-heptene compound (III). 33 g (III) in 100 ml ethanol, 6 g Raney- Ni,1500 PSI hydrogen,150øC to get 26 g of the 2- heptane (IV). 26 g (IV), 118 ml 57% hydrogen iodide; add 156 ml acetic anhydride and heat at 155o C for two hours to get 22 g of the resorcinol.
5-Alkyl Resorcinals BER 69,1644(1936)
25g ethyl-3,4,5-trimethoxybenzoyl acetate and 2.1 g Na in 100 ml ethanol; warm to react. Add 2 g n-propyl iodide (or n-amyl iodide, etc.) and heat twelve hours on steam bath; neutralize and distill off the ethanol. Extract with ether and dry, evaporate in vacuum to get about 32 g of the alkyl acetate (I). Heat 22 g (I) in 5% KOH in ethanol for one hour at 50øC to get 14 g 3,4,5-trimethoxyvalerophenone (II), which crystallizes on standing. 11 g (II), 600 ml ethanol, 60 g Na; warm and after Na is dissolved, add 2 L water. Acidify with HCl, distill off the ethanol and extract with ether. Dry, evaporate in vacuum the ether to get 7.8 g olivetol dimethyl ether (or analog) (III). 7.2 g (III), 70 ml hydrogen iodide; boil two hours and distill (164/760) to get Olivetol.
Olivetol HCA 52,1132(1969)
Reduce 3,5-dimethoxybenzoic acid with lithium aluminum hydride to 3,5- dimethoxybenzyl alcohol (I). to 10.5 g (I) in 100 ml methylene chloride at 0ø C add 15 g PBr3; warm to room temperature and stir for one hour. Add a little ice water and then more methylene chloride. Separate and then dry, evaporate in vacuum the methylene chloride. Add petroleum ether to precipitate about 11.5 g of the benzyl bromide (II). To 9.25 g (II), 15 g CuI, 800 ml ether at 0ø C, add butyl (or other alkyl)-Li (16% in hexane), and stir for four hours at 0ø C. Add saturated NH4Cl and extract with ether. Dry and evaporate in vacuum the ether (can distill 100/0.001) to get about 4.5 g olivetol dimethyl ether (III) or analog. Distill water from a mixture of 90 ml pyridine, 100 ml concentrated HCl until temperature is 21 0øC. Cool to 140øC and add 4.4 g (III); reflux two hours under N2. Cool and pour into water. Extract with ether and wash with NaHCO3. Make pH 7 and dry, evaporate in vacuum to get 3.8 g olivetol which can be chromatographed on 200 g silica gel (elute with CHCl3) or distill (130/0.001) to purify.
5-Alkyl Resorcinols TET 23,77(1967)
Since the method as given originally leads to 4-alkyl resorcinols which do not produce an active THC, it is here modified to give the 5-alkyl isomers. The method is illustrated for 1.2-dimethyl-heptyl resorcinol which gives a much more active THC than olivetol. Convert 3,5- dihydroxyacetophenone (5-acetyl resorcinol) to 3,5- dimethoxyacetophenone(I) in the usual way with dimethylsulfate.
To 24 g Mg, 1 crystal 12, 100 ml ether, add dropwise under N2, 180 g 2- Br-heptane in 100 ml ether over one hour and then reflux two hours. Add over 1 1/2 hours a solution of 90 g (I) in 200 ml tetrahydrofuran and reflux 10 hours. Cool and add 180 ml saturated NH4Cl; decant the solvents and extract the residue with tetrahydrofuran. Combine the solvents and the tetrahydrofuran and dry, evaporate in vacuum. Add a few drops 20% sulfuric acid to the residual oil and evaporate in vacuum the water (oil bath temperature 120-130øC/10mm). Distill the oil at oil bath temperature 285øC/0.2. Fraction boiling 128-140/0.2 yields about 60 g 2- (3,5-dimethoxyphenyl)-3-methyl-2-octene(II). If saponified and used to synthesize a THC, this might give an active product, thus disposing of the necessity of the next step. Hydrogenate 50 g (II) in 100 ml ethanol, 2-3 atmospheres H2, 0.6 g 10% Palladium-Carbon catalyst for two hours, or until no more H2 uptake (or use the NaBH4-Ni method described at the start). Filter and dry, evaporate in vacuum, and distill the residual oil (110-17/0.1) to get 42g of the octane (III). 40 g (III), 100 ml 48% HBr, 320 ml glacial acetic acid and reflux four hours. Pour on ice and take pH to 4.5 with 10 N NaOH and extract with ether. Extract the ether with 3x150 ml 2N NaOH; acidify the combined NaOH extracts with glacial acetic acid and extract with ether. Dry and evaporate in vacuum, and distill the oil ( 159/0.1 ) to get 20 g 5-1, 2-dimethylheptyl resorcinol.
5-Alkyl Resorcinols JACS 61,232(1939)
Convert benzoic acid to 3,5-dihydroxybenzoic acid (alpha-resorcyclic acid) (I). 50 g (I), 134 g dimethylsulfate, 60 g NaOH, 300 ml water; add 35 g NaOH and reflux to obtain about 50 g 3,5-dimethoxybenzoic acid (II) which is converted to dimethoxybenzoyl chloride (III) with PCl5. Extract the (III) with ether and filter. Saturate the ether with NH3 at 0øC and filter. Wash with ether and water and recrystallize from hot water to get 3,5-dimethoxy-benzamide (IV). To a solution of 1 M of n-hexyl bromide (or 1,2-dimethylheptyl bromide, etc.) add 24.3 g Mg in 200 ml ether to prepare the Grignard reagent. Then rapidly add 46 g (IV); add 300 ml ether and reflux and stir two days, excluding moisture and air. Add a mixture of ice and water and 80 ml concentrated sulfuric acid. Separate and dry, evaporate in vacuum the ether layer to get about 50 g of the dimethoxyalkyl benzyl ketone (V). Recrystallize from dilute ethanol. Add 0.2 M (V), 20.8 g 100% hydrazine hydrate, 75 ml ethanol; reflux six hours. Evaporate in vacuum and heat the residual oil with 82 g powdered KOH in oil bath about 225øC until N2 evolution ceases. Can distill or recrystallize from 95% ethanol to get the dimethoxyalkyl benzene (VI). 0.025 M (VI), 40 ml glacial acetic acid, 15 ml 48% HBr; reflux four hours and pour into ice water; decolorize with a little Na bisulfite, neutralize with NaHCO3 and extract with ether. Wash the extract with 10% NaOH and separate and acidify the basic solution. Extract with ether and dry, evaporate in vacuum the extract to get the 5-alkyl resorcinol. Distill or recrystallize from water to purify. Dry, evaporate in vacuum the first ether extract to recover starting material.
Olivetol LAC 630,77(1960), JCS 311(1945), cf. JACS 89,6734(1967)
Dissolve 100 g malonic acid in 360 g dry pyridine and heat 48-52øC for forty hours with 100 g n-hexaldehyde (n-capronaldehyde) or homolog. Cool in ice bath and with good stirring add dropwise 150 ml ice cold concentrated sulfuric acid (keep temperature below 5øC). After addition add water to dissolve the precipitate and extract with ether two times. Dry, evaporate in vacuum the ether and distill (70/0.7 or 102/5) to get about 98 g 2-octenoic acid (I). 95 g (I) in 300 ml ether; cool to -5øC and slowly add a solution of an excess of diazomethane in ether dried over KOH and let react for about one hour. Let stand twelve hours, evaporate in vacuum and distill (91/17) to get about 94 g clear methyl- 2-octenoate (II). To 16.3 g Na in 210 ml ethanol add 93 g ethyl- acetoacetate (ethyl-3-oxo-butanoate), heat to boil and add dropwise 92 g (II) over 20 minutes. Stir and reflux five hours and cool to precipitate.Filter, wash with ethanol and dissolve precipitate in 800 ml water. Cool to 0ø C and slowly add 80 ml ice cold concentrated HCl to precipitate. Filter, wash with water and ligroin to get about 108 g 6- carbethoxy-4,5-dihydro-olivetol (III) (recrystallize from petroleum ether). To 104 g (III) in 260 ml glacial acetic acid at room temperature with good stirring, add dropwise over one hour 69 ml Bromine. Heat four to five hours at 60o C, cool and add 300 ml water and let stand twelve hours. Oil separates which will precipitate on agitation and rubbing. Filter, wash with water until colorless (recrystallize from ligroin, recrystallize from glacial acetic acid and precipitate with water) to get about 86 g 6-carbethoxy-2,4-dibromo- olivetol (IV). 0.035 g Palladium-Carbon catalyst in 25 ml hydrogenation bottle. Saturate with H2 (pressure - 2.8 Kg/cm2) and add 0.33g (IV) in 5 ml glacial acetic acid, which takes up 39.5 cm3 H2 at atmospheric pressure over 1 1/2 hours at 60-70øC. Filter and acidify at 0øC with ice cold 6N HCl. Extract with ether and dry, evaporate in vacuum. Recrystallize the oil from ligroin and then from glacial acetic acid by adding water to get about 0.2 g 6-carbethoxyolivetol (V). (IV) can also be hydrogenated at room temperature and atmospheric pressure over 1/2g Palladium-Carbon catalyst by dissolving 70 g in 500 ml 1 N NaOH. Heat 35 g (V) with 45 g NaOH in 170 ml water for two hours or until no more CO2 is evolved. Cool, acidify with 6N HCl and boil 3 minutes. Extract the oil with ether and dry, evaporate in vacuum the ether (can distill on Vigreux column 123/0.01, oil bath 160o C) and let oil stand in refrigerator until crystalline to get about 21 g olivetol. See CA 70,77495t(1969) for another variant of this procedure.
1',1'-Dimethyloliuetol HCA 52,1127(1969)
Prepare 3,5-dimethoxy benzyl alcohol by reducing the acid with lithium aluminum hydride as described elsewhere here, by hydrogenating the aldehyde (2-3 atmospheres H2, room temperature, PtO2 in ethanol -- or by the NaBH4 method), in five steps as described in JACS 70,666(1948), or prepare (II) directly by the diborane procedure. Add with stirring 22.5 g SOCl2 in 100 ml ether in 20 ml portions to a solution of 15 g 3,5- dimethoxybenzyl alcohol, 1 ml pyridine and 200 ml ether. Let stand and wash with 2x100 ml cold water; separate and dry, evaporate in vacuum the ether to get 16 g 3,5-dimethoxybenzyl chloride (I). Recrystallize from petroleum ether. 16 g (I), 300 ml ethanol, 30 g NaCN, 75 ml water; reflux three hours and pour onto 400 g ice. After ice melts, filter and recrystallize precipitate from petroleum ether to get about 14 g 3,5- dimethoxybenzyl CN (II). 5 g 50% NaH in mineral oil; wash three times with pentane or hexane; fill flask with N2 or argon and add dimethoxyethane or dimethylformamide (freshly distilled from K if possible). Stir and add 9 ml methyl iodide. Carefully add 8 g (II) and stir twelve hours. Add ice water and neutralize with NaHCO3 to pH 7-8. Extract with ether and dry, evaporate in vacuum the ether (can distill 170/0.1 ) to get about 9 g alpha, alpha-dimethyl-3,5- dimethoxyphenylacetonitrile (III). Add 1.5 g (III) to a solution of 0.45 g Mg, 2.5 g n-propyl Br (freshly distilled if possible) in 30 ml ether. Reflux sixty-five hours. Add 2N sulfuric acid and heat two hours on water bath. Cool and extract with ether and dry, evaporate in vacuum (can distill 135/0.001) to get about 1.75 g 2-methyl-2-(3,5- dimethoxyphenyl) hexanone-3 (IV). Dissolve 4g (IV) in 50 g ethane dithiol and saturate at 0øC with HCl gas (take care to exclude water). Stir the solution in a sealed container forty-eight hours at room temperature and then basify with NaHCO3. Extract with ether and dry, evaporate in vacuum (or dry and evaporate in vacuum two hours at 70/12 and distill at 130/0.001 ) to get about 5 g of the thioketal (V). Reflux 5.3 g (V),100 g Raney-Ni, 2 L ethanol (or use NaBH4 procedure) for thirty hours. Cool and filter (Celite), evaporate in vacuum and distill residue (115/0.001) to get 3.7 g of the hexane which is saponified as described for the dimethyl ether of olivetol above to give about 2.5 g of the title compound (can distill 150/0.001).
Olivetol ACS 24,716(1970)
Prepare 3,5-dimethoxybenzoic acid as described elsewhere here, and to a solution of 18.2 g in 250 ml dry tetrahydrofuran under N2, add 1 g 85% LiH, stir for fourteen hours and then reflux for one-half hour. Add a solution of about 1.3 M butyllithium in ether (Org. Rxns. 6,352(1957)) with stirring and ice cooling until the reaction mixture gives a positive Gilman test (JACS 47,2002(1925)). Then add 500 ml ice water, extract with ether and dry, evaporate in vacuum the organic phase to get a yellow oil which is dissolved in an equal amount of absolute ethanol; left in refrigerator twelve hours to precipitate. Filter and evaporate in vacuum the ethanol to one-half volume to give more precipitate for a total of 18 g 1-(3,5-dimethoxyphenyl)-1 pentanone (I). 5.64 g (I) in 200 ml methanol; 0.66 g 20% Pd(OH)2 on carbon (TL 1663( 1967)) and hydrogenate at room temperature and atmospheric pressure over two to three hours (or use other reducing method as described here).Filter and evaporate in vacuum to get olivetol dimethyl ether (II). 4.88 g (II), 40 ml HI (density 1.7, decolorized with red phosphorous) and stir three hours at 115-125øC under N. Dry, evaporate in vacuum or pour into 100 ml ice water and extract with methylene chloride; wash methylene chloride with water and dry, evaporate in vacuum (can distill 160-170/3-4) to get 3.5 g olivetol.
5-Alkyl Resorcinols JOC 33,687(1968), JACS 71,1624,1628(1949) Illustrated for 1,2-dimethylheptyl compound
110 g powdered 3,5-dimethoxybenzamide (preparation given elsewhere here), five times excess of MethylMgI and reflux sixteen hours. Add 1.2 L concentrated HCl and 1200 g ice and let stand sixteen hours with occasional shaking. Extract with ether, dry, evaporate in vacuum and distill (115-128/0.3). Let stand in refrigerator to precipitate. Wash precipitate with petroleum ether and recrystallize from petroleum ether to get about 60 g 3,5-dimethoxyacetophenone (I). 83 g (I) in 50 ml methanol. Add dropwise with stirring to solution of 18 g NaBH4 in 300 ml methanol and 1 g NaOH. Reflux 30 minutes and concentrate by distilling. Add about 100 ml water during distillation. Evaporate the methanol, cool and extract with ether. Dry, filter, concentrate, and distill (124/0.65) to get about 80 g 3,5-dimethoxyphenyl ethanol (II).18 ml PBr3 in 70 ml ether; add dropwise with stirring over one hour to 28.5 g (II) in 70 ml ether cooled in an ice bath. Warm to room temperature; reflux two hours on steam bath; cool and pour into 200 g ice. Shake and extract with ether 3 times; wash ether with l0oþo NaHCO3 and water and dry, filter. Concentrate on steam bath and then add with stirring under anhydrous conditions to 42 g diethyl-n-amylmalonate in 300 ml ethanol in which has been dissolved 4.6 g Na metal. Stir 1 1/2 hours at room temperature and then heat to distill off the ether and complete the reaction. When the distillation head temperature reaches 78øC add water and continue distilling until temperature reaches 99øC. Cool and extract with 3x250 ml ether and evaporate in vacuum the ether. Dissolve residue in 180 ml ethylene glycol and 35 g NaOH by stirring six hours at 160øC. Cool and add 1500 ml water and wash with ether. Acidify the aqueous phase and extract with 4x200 ml ether. Evaporate in vacuum the ether or evaporate on steam bath and dissolve the residue in 150 ml xylene. Evaporate residual ether and water until head temperature reaches 140o C and reflux six hours. Evaporate in vacuum to get about 30 g oily alpha-amyl- beta-methyl-hydro-cinnamic acid (III). 14.5 g (III), 5 g lithium aluminum hydride, 250 ml ether; reflux 6 hours. Cool and carefully add methanol, water and dilute HCl. Separate the aqueous layer, saturate with NaCl and extract with ether. Wash ether with NaHCO3 (acidify NaHCO3 extract to precipitate starting material) and dry, evaporate in vacuum the ether to get about 12 g 2-amyl-3(3,5-dimethoxyphenyl)-butanol (IV). 1 I.7 g (IV) and 8.5 g p-toluenesulfonyl Cl each dissolved in 20 ml pyridine. Cool in ice bath and combine. Place in freezer about sixteen hours, pour over ice and extract with ether. Wash ether with cool, dilute HCl until HCl extract is acidic. The combined HCl extracts are then acidified and extracted with ether. Wash the ether with NaHCO3, dry and then add dropwise with stirring to 3 g lithium aluminum hydride in 75 ml ether. Reflux 4 1/2 hours and work up as for (IV). (Can chromatograph the undistilled product on activated alumina and elute with 600 ml petroleum ether, then 200 ml methanol; concentrate and distill (94/0.001) the petroleum ether to get product; concentrate the methanol to give starting material). Yield is about 8 g 2-(3,5- dimethoxyphenyl)-3-methyl-octane (V). Convert (V) to the title compound by refluxing in 48% HBr in glacial acetic acid as described elsewhere here.
An alternative route from (II) to (V) involves adding (II) and diethylmethylmalonate to prepare dimethyl-3,5-dimethoxyhydro-cinnamic acid as described for the preparation of (III). Then dehydrate and hydrolyze to dimethyl-3,5-dimethoxycinnamic acid which is hydrogenated to the alcohol and converted in several steps to (V).
5-Alkylresorcinols Aust. J. Chem. 21,2979(1968)
Reflux 6.9 g triphenylphosphine and 6.6 g lauryl bromide (or equimolar amount of homolog) in 40 ml xylene for 60 hours. Remove solvent and wash residue with 5x20 ml ether (by decanting) to get 11 g lauryl triphenylphosphonium bromide (I). To a stirred suspension of 5.6, g (0.011M) (I) in 50 ml ether add 0.01M butyllithium solution (see Organic Reactions 8,258(1954) for preparation). Stir 1/2 hour at room temperature and slowly add 1.66 g 3,5-dimethoxybenzaldehyde (preparation given elsewhere here) in 10 ml ether over 1/2 hour. After 15 hours, filter, wash filtrate with water and dry, evaporate in vacuum. Dilute residue with pentane, filter and remove solvent. Dissolve the residual oil in 25 ml ethyl acetate and hydrogenate over 0.1 g Adams catalyst at one atmosphere and room temperature for 2 hours. Filter and evaporate in vacuum to get the 5-alkylresorcinol dimethyl ether which can be recrystallized from pentane and demethylated as described elsewhere here.
5-Alhylresorcinols Aust. J. Chem. 21,2979( 1968)
Add 2.17 g 3,5-dimethoxybenzoyl chloride (see BER 41, 1329 (1980) or elsewhere here for preparation) in 2.5 ml ether over 10 minutes to a stirred solution of 0.42g diazomethane and 1.01 g triethylamine in ether at -5øC. Keep 10 hours at 0øC, filter, wash precipitate with 20 ml ether and evaporate in vacuum the combined filtrates to get 1.9g diazo-3,5- dimethoxyacetophenone(I). Recrystallize from benzene-cyclohexane. To 1.5g(I) in 15 ml ethanol add 1.23g pyridinium perchlorate in 2 ml pyridine. Reflux 2 hours, cool and add 5 ml water. Filter to get 1.5g 3,5-dimethoxyphenylacyl pyridinium perchlorate (II). Recrystallize from ethanol. To a stirred suspension of 0.13 g Na hydride in 10 ml dry, acid free dimethylacetamide at 10øC under nitrogen, add 1.79g (II) in 10 ml dimethylacetamide and shake for 15 minutes. Add 0.0075M propyl iodide or homolog and keep 12 hours at room temperature. Heat 2 hours at 90øC and cool to room temperature. Add 3g zinc dust and 5 ml glacial acetic acid; stir at room temperature four hours and filter. Add 20 ml water to filtrate and extract with 50 ml ether. Wash the ether layer with 2x50 ml 10% K2CO3, 50 ml water and 20 ml saturated NaCl. Dry and evaporate in vacuum to get oily 3,5-dimethoxyphenylbutyl ketone (can chromatograph on 50 g alumina and elute with 3:1 petroleum ether:ether). Recrystallize from ethanol. Hydrogenolysis (see Aust. J. Chem. 18,2015(1965) or elsewhere here) gives the olivetol dimethyl ether.
5-Alkylresorcinols Aust. J. Chem. 24,2655(1971)
The method is illustrated for olivetol preparation, but substituted thiophens can be used to get olivetol homologs. To a stirred solution of 45g 3,5-dimethoxybenzoyl chloride and 17.4g thiophen in 300 ml benzene at 0øC, add dropwise 10.5g freshly distilled stannic chloride. Stir one hour at room temperature and add 200 ml 3% aqueous HCl. Separate the benzene layer and wash the aqueous layer with benzene. Dry and evaporate in vacuum the combined benzene layers and distill the red residue (250øC bath/4.5) to get 45g 2-(3,5-dimethoxybenzoyl) thiophen(I). Recrystallize from petroleum ether. Add a solution of 21 g AlCl3 in 160 ml ether to a stirred suspension of 6.1 g lithium aluminum hydride in 140 ml ether. After 5 minutes add a solution of 39g(I) in 300 ml ether at a rate giving a gentle reflux. Reflux and stir 1 hour; cool in an ice bath and treat dropwise with 50 ml water, then 50 ml 6N aqueous sulfuric acid. Separate the layers, extract the aqueous layer with 3x100 ml ether and dry, evaporate in vacuum the combined ether layers. Can distill the residue (230øC bath/5mm) to get 27g oily 2-(3,5-dimethoxybenzyl) thiophen (II). Recrystallize from petroleum ether. Reflux a solution of 5g (II) in 700 ml ethanol with W-7 Raney Nickel prepared from Ni-Al alloy (see Org. Synthesis Coll. Vol III,176(1955)) for 6 hours. Filter, evaporate in vacuum and can distill (140/0.01) to get about 2.2g oily olivetol dimethyl ether which can be reduced to olivetol as described elsewhere here. The use of the novel reduction methods described at the beginning of this section would render this method much simpler.
5-Alkylresorcinols German Patent 2,002,815 (30 July 1970)
In a 2 liter, 3 necked flask with a stirrer, dropping funnel, thermometer, reflux head, nitrogen stream and mercury manometer (if available) stir 230 ml dry methanol and 32.4g sodium methoxide under nitrogen until dissolved. Add 110g diethylmalonate and stir 10 minutes. Add portionwise 75g 90% pure 3-nonene-2-one (for olivetol-preparation below) keeping the temperature below the boiling point (50-60øC). Stir and reflux 3 hours, then cool to room temperature, neutralize with about 50 ml concentrated HCl and let stand overnight. Evaporate in a vacuum and dissolve the residue in 200 ml 1N HCl and 800 ml ethylacetate. Separate and wash the ethylacetate with 2x300 ml water and extract with saturated NaHCO3 until a small portion gives no turbidity upon acidification (about 5x200 ml). Carefully acidify the combined NaHCO3 extracts and then extract with 3x300 ml ether. Dry and evaporate in vacuum the ether (can dry under vacuum several days) to get 6-n-pentyl- 2-OH-4-oxo-cyclohex-2-ene-1-methyl- carboxylate(I). 4.8 g (I) and 100 ml glacial acetic acid are stirred vigorously at 75øC until dissolved. Cool and keep temperature between 5 and 10øC while adding a solution of 3.9g bromine in 10 ml glacial acetic acid dropwise over 1 hour. Stir 1 hour at room temperature then 3 hours on a steam bath. Evaporate in vacuum and dissolve the residual oil in 200 ml ether. Wash with 2x25 ml 10% sodium dithionite, 2x25 ml saturated NaHCO3 and water and dry, evaporate in vacuum to get olivetol (or analog) (can distill at 125-130/0.05). Alternatively, to 4.8g (I) ad 5.6g iodine in 200 ml glacial acetic acid. Stir and reflux 10 hours, evaporate in vacuum, dissolve residue in 250 ml ether and proceed as above to get olivetol. A third alternative is to stir 12.2g (I) in 100 ml glacial acetic acid at 25øC with vigorous stirring until well suspended. Cool and keep temperature at 5-10øC while adding dropwise 22.4g cupric bromide dissolved in 25 ml glacial acetic acid over 1 hour. Stir 1 hour at room temperature then 3 hours on a steam bath and evaporate in vacuum. Dissolve the residue in 200 ml water and 300 ml ether. Wash the ether layer with 2X50 ml 10% sodium dithionite, 2x35 ml saturated NaHCO3 and 75 ml water and dry, evaporate in vacuum to get olivetol (or analog).
For the 1,2-dimethylheptyl homolog proceed as follows.
Combine 15g 5,6-dimethylundec-3-ene-2-one with 19g diethylmalonate as described above to get (I). Brominate 20.2g (I) with 12g bromine over 2 hours as described and stir 1 hour at room temperature. Add 500 ml water and let stand overnight at 5-10øC. Filter, wash precipitate with about 4x75 ml cold water and dry in vacuum at 50øC to get 26g 3-bromo-2-OH-4-oxo-6- (1,2-dimethylheptyl)-cyclohex-2-ene-1- methylcarboxylate(II). In a 3 liter 3 necked flask with a stirrer, thermometer, reflux head and Dean-Stark trap, add 350g (II) and 522g pyridine hydrochloride and heat on oil bath at 90øC 4 hours. Heat with the heating mantle (removing volatiles with the Dean-Stark trap) until the internal temperature reaches 190- 200øC and hold at this temperature 2 hours. Cool to room temperature and shake with 3 liters ether and 660 ml 1.2N HCl and then 2x300 ml water. Extract the ether solution with 4x350 ml 10% NaOH and then extract the combined NaOH extracts with 2x300 ml ether. Acidify the alkaline solution with about 700 ml concentrated HCl and extract with 3x800 ml ether. Wash the combined ether extracts with 3x300 ml 10% sodium dithionite, 2x300 ml saturated NaHCO3 and 300 ml water and dry, evaporate in vacuum the ether to get the 5-(1,2-dimethyl- heptyl) resorcinol.
To prepare the 3-nonene-2-one condense excess acetone with n-hexaldehyde (or 2,3-dimethyloctanal for 5,6-dimethyl-undec-3-ene-2-one) in the presence of NaOH in an inert medium if desired (benzene, toluene, xylene, etc.), at 10-70øC to get (I). Dehydrate (I) with sodium sulfate or cupric sulfate in an inert medium at reflux temperature or simply reflux in benzene, xylene or toluene.
5-Alkylresorcinols JOC 37,2901(1972) For 5-alkylresorcinols see Chem. and Ind. 685( 1973) also.
This is an improved version of a previously given synthesis (LAC 630,71 (1960)). The ethanol used is distilled from Ca ethoxide; dimethoxyethane from potassium. Cupric bromide is produced from cupric oxide and 5% excess of HBr, plus sufficient bromine to remove the milkiness on addition of a drop of the mixture to water; concentrate and dry, evaporate in vacuum over KOH flakes. 650g (5.3M) ethyl chloroacetate and 880g (5.3M) triethyl phosphite are mixed and placed in a 3 liter flask fitted with a thermometer and condenser under nitrogen. Heat and stir and slowly bring to 125øC. Discontinue heating as ethyl chloride evolution proceeds over 1/2 hour. Heat to 160øC over a 75 minute period and keep at 160o C 8 hours. Cool,distill (e.g., through 12" Vigreux column) (74-7/0.03) to get 96% yield of triethylphosphonoacetate (I). In a 3 liter flask fitted with a stirrer, dropping funnel and condenser, place 45.3g NaH (1M in mineral oil) and 1 liter of dry ether. Flush with nitrogen and keep at positive nitrogen pressure. Stir in ice bath while 224 g (1M) (I) is added dropwise over 75 min. Stir and reflux 1 hour (H2 evolution stops). Cool in ice-salt bath and add 1M of aldehyde (e.g., hexaldehyde for olivetol) over 1 hour. Continue to cool and stir an additional 10 minutes and then slowly bring to reflux and reflux for 10 minutes (ppt. prevents stirring). Decant the ether and dissolve the oil layer in 500 ml warm water and separate the upper organic layer. Extract the aqueous layer with 200 mI ether and extract the combined organic solutions with 200 ml saturated NaHCO3. Dry and evaporate in vacuum (can distill) to get the ethyl-á-alkylacrylates in about 90% yield (II). In a flask with nitrogen and fittings as in preceding step, add 156 g ethyl acetoacetate to Na ethoxide from 25.3g Na and 500 ml dry ethanol, and stir and reflux 1/2 hour. Add 1M of (II) dropwise over 90 minutes and reflux 20 hours. Cool in ice, filter, wash ppt. with 500 ml ice cold absolute ethanol and several times with portions of ether and dry, evaporate in vacuum to get the dione Na salt (III) in about 80% yield (for olivetol precursor). In a 250 ml flask place 0.1 M (III),100 ml 1,2-dimethoxyethane and flush with nitrogen and stir at room temperature while 45g of cupric bromide is added portionwise over 5 minutes, under a nitrogen stream. Stir 1/2 hour and then reflux and stir 1 hour. Cool and evaporate (keep temperature below 50øC) but do not remove more than about 65 ml dimethoxyethane. Dilute the remaining solution with 200 ml benzene and filter. Wash the ppt. with 50 ml benzene and evaporate the combined benzene filtrates (keep temperature below 50øC). Dissolve the bromodione in 100 ml dimethylformamide and put in 500 ml flask under nitrogen. Stir and heat slowly until reflux and then heat to 150øC and reflux 4 hours. Cool, pour into 500 ml water, extract with 3x100 ml dichloromethane and dry, evaporate in vacuum to get the ethyl-6-alkyl- 2,4-dihydroxybenzoate (IV). Add a solution of 24g NaOH in 200 ml water to (IV) and stir and reflux under nitrogen in hood for 3 hours. Cool in ice bath, acidify carefully with a cold solution of 20 ml concentrated sulfuric acid in 80 ml water while stirring under nitrogen in ice bath. Reflux under nitrogen 5 minutes, cool, extract 3 times with ether and dry, evaporate in vacuum the combined extracts to get about 80% yield of olivetol (or analog). The last step may not be necessary since (IV) may yield an active THC.
Dimethylheptylresorcinol CA 65,20062(1966)
This method is specifically designed to produce good yields of dimethylheptylresorcinol, which provides, after synthesis by any of the various routes, one of the most active THC analogs yet discovered. Note that the synthesis may not have to be carried all the way to the alkylresorcinol since the intermediate ketones etc. may give an active THC analog. Mix 294g (1.6M) 1,3,5-trichlorobenzene, 184g (3.4M) Na methoxide and 450g (3 3M) diglyme and reflux at 162øC for 42 hours. Cool to room temperature, filter and distill the solvent to get 70% yield of 1-Cl-3,5-dimethoxybenzene (I). 43.2g (I) in 540 ml tetrahydrofuran is added dropwise to 7.3g Mg, a small crystal of iodine and a few drops of ethyl bromide (under nitrogen if possible) over 1/2 hour while the mixture is heated to 75øC. Reflux 2 hours and cool to room temperature to obtain the Grignard solution. To anhydrous liquid ammonia in a cooled flask, add Fe(NO3)3*9H2O and then small pieces of sodium and bubble air through the solution until reaction is observed. Add more sodium portionwise until 11.5g is in solution. To the solution at its reflux temperature, add 27.6g (0.5M) proprionitrile (or isobutyronitrile etc. for analogs) and add the resulting solution dropwise to 53.3g 1-Cl- pentane (or 0.5M analog such as 2-Br-hexane etc.) and let the ammonia evaporate. Add ether, then water to the residue and separate the aqueous layer and extract with ether. Dry and evaporate in vacuum the combined ether solutions to give 64% yield of 2-methyl-heptanonitrile (II) (or analog). Add 34.0g (0.27M) (II) in tetrahydrofuran to the Grignard solution of (I) over 1/2 hour, heat 6 hours at 60øC and hydrolyze with 1600 ml 50% sulfuric acid, keeping the temperature below 40øC. Evaporate in vacuum the solvent and add another 400 ml 50% sulfuric acid. Heat 1 hour at 95-100øC, cool, add ether, separate the aqueous layer and extract with ether. Dry and evaporate in vacuum the combined ether layers to get 71% yield 2-(3,5-dimethoxybenzoyl) heptane (III) (can distill 133-8/0.2), which can be demethylated as described for the preparation of (VII) below and possibly used to synthesize an active THC analog (as can IV, V, or VI). 21.8g (0.082M) (III) is added dropwise (keeping the temperature at 15-20øC) to 3 molar methyl-MgBr in ether and refluxed 1 hour. Pour into a sulfuric acid-ice mix, add more sulfuric acid and stir. Separate and extract the aqueous layer with ether. Wash, dry, filter and evaporate in vacuum the combined ether layers to get 2- (3,5-dimethoxyphenyl)-3-methyl- octanol (IV), which is dehydrated by mixing with anhydrous oxalic acid and heating to 130-40øC. Extract the dehydrated reaction products with benzene to get the octenes (V). Add 25g (V), 2.5g 65% Ni on kieselguhr in dry hexane to hydrogenator and hydrogenate at 1750 psi and gradually increase the temperature to 125o C. After 3 hours, increase the pressure to 1850 psi and hold there 2 1/2 hours. filter and evaporate in vacuum to get 2-(3,5-dimethoxyphenyl)-3- methyl-octane (VI). Add 20g (0.08M) (VI) to 38% HBr in glacial acetic acid and stir and reflux for 6 hours. Pour onto ice and water, neutralize with solid sodium carbonate and extract with ether. Extract the ether with 10% aqueous NaOH, acidify the aqueous solution with HCl, extract with ether and dry, evaporate in vacuum (can distill) to get 2- (3,5-dihydroxyphenyl)-3-methyl- octane (VII) (5-(1,2-dimethylheptyl)- resorcinol). As an alternative process for getting from (III) to (VI), combine 64.2g (0.18M) methyltriphenylphosphonium bromide in dry benzene with 11.6g (0.18M) (in 14% solution) butyllithium in benzene. Heat to 60øC and cool. 49.0g (0.176M) (III) in 40 ml dry benzene is added (keep temperature below 40øC) and then reflux 2 hours. Cool, filter and evaporate in vacuum to get the octene, which after catalytic hydrogenation as described for (V) yields (VI).
5-A Alkylresorcinols Aust. J. Chem. 21,2979(1968)
Mix 50g 3,5-dihydroxybenzoic acid, 250 g K2CO3, 200 ml dimethylsulfate and one liter acetone and reflux 4 hours. Remove the acetone, add one liter water and one liter ether to the residue and extract. Wash the ether extract with 2x100 ml concentrated NH4OH, 2x100 ml dilute HCl and 100 ml water and dry, evaporate in vacuum to get 48g methyl-3,5- dimethoxybenzoate (I). Recrystallize from aqueous methanol. To a stirred suspension of 19g lithium aluminium hydride in 200 ml ether add 78.4g (I) in 300 ml ether at a rate which gives gentle refluxing. Reflux 2 1/2 hours, cool and add 50 ml wet ether; then 100 ml dilute sulfuric acid. Wash and dry, evaporate in vacuum the ether extract to get 62g oily 3,5- dimethoxybenzyl alcohol (II). Recrystallize from ether-pentane. To a cooled stirred slurry of 15g CrO3 and 250 ml pyridine add 8.4g (II) in 25 ml pyridine and let stand 1 hour at room temperature. Add 60 ml methanol, let stand 2 hours, and dilute with 500 ml 5% NaOH and 500 ml ether. Extract the aqueous layer with ether and wash the combined ether layers with 500 ml water, 3x500 ml 5% sulfuric acid, 500 ml water and 200 ml saturated NaCl and dry, evaporate in vacuum to get 7g 3,5- dimethoxybenzaldehyde (III). Re-crystallize from ether-pentane. To a flask with a dropping funnel and condenser add 0.58g Mg turnings and 10 ml ether. Add a few drops of a solution of lauryl bromide (5.7g) or equimolar amount of homolog in 15 ml ether and start reaction by adding 2 drops methyl iodide. Add the remaining bromide solution with stirring and gentle refluxing over 15 minutes and then reflux 3 hours. Cool in an ice bath and add 3.1g (III) in 5 ml ether dropwise with stirring over 45 minutes. Reflux 4 hours, cool and dilute with ice water. Wash the organic layer with 2x25 ml 3N sulfuric acid, 2x25 ml 10% K2CO3, 25 ml water, 25 ml saturated NaCl and dry, evaporate in vacuum to get 5g 3,5- dimethoxyphenyldodecyl methanol (IV) or homolog. Recrystallize from methanol. Hydrogenate 4.2g (IV) in 50 ml ethyl acetate with 5 drops concentrated sulfuric acid and 0.5g 10% Palladium-Carbon catalyst at room temperature and 5 atmospheres hydrogen for 4 hours. Filter and evaporate in vacuum to get the aklylresorcinol dimethyl ether. Aust. J. Chem. 26,799(1973) gives a 2 step synthesis of 5-alkylresorcinols by condensation of beta-ketosulphones with 3,5-dimethoxybenzyl bromide and then reduction. Aust. J. Chem. 26,183(1973) gives a synthesis from 3,5- dimethoxy-N,N-dimethylbenzylamine in 7 steps (but perhaps only 4 will reach a cpd. that can give an active THC analog).
5-alkylresorcinols CPB 20,1574(1972)
To a solution of 0.02M ethyl-á-ketocaprylate (or homolog) in 20 ml tetrahydrofuran, add 1.02g (0.02M) (53% oil) NaH with stirring and cooling and then add a solution of diketene (1.68g, 0.02M) in 20 ml tetrahydrofuran dropwise, keeping the temperature between -5 and 0øC. Stir 1 hour at this temperature and then 1 hour at room temperature. Neutralize with 10% HCl and extract with ether. Dry and evaporate in vacuum to get about 38% yield of ethyl-olivetol carboxylate (I). (I) can be purified on silica gel, the impurities being eluted with petroleum ether (30-35øC) and the produce with 8:1 petroleum ether:ether. Recrystallize from n-hexane. Dissolve 0.2g (I) in 10 ml 10% NaOH and reflux 30 minutes. Acidify with 10% HCl and extract with ether. Wash the extract with water and dry, evaporate in vacuum (can distill 126-129/3) to get 96% olivetol (or homolog)
For new, simple, high yield syntheses of 5-alkyl resorcinols see TL 4839(1973), 2511 (1975) and CJC 52:2136(1974). A superior, high yield, 3 step synthesis of olivetol and analogs has recently appeared in JOC 42:3456(1977).