Mushroom Odors Student Synthesis of the Odoriferous Compounds of the Matsutake Mushroom William F. Wood a n d Mark Fesler Humboldt State University. Arcata, CA 95521 T h e matsutake mushroom. Tricholoma matsutake, is a highly prized culinary delicacy in J a p a n and in seasun it is a must in many traditional fuods. This mushroom cannot be culti\,ated and is har\,ested ann~mllyfrom the pine forests in .hpan. In recent years Japanese productiun of this mushromn has decrrnsed, sg, large numbers of this mushroom a r e imported from Korea and the United Sta1rs.l T h e demand ior marsutnke mushrooms is due t o its pleasant and appetizing flavor or aroma. Some of t h r ,lapunese dishes that rely on this tasty mushroom a r e matsutake rice (matsutake gohan), mushroom barheque (yaki matsutake), and a soup known as mushrooms-in-a-tea~ot(dobin mushi). . Two odoriferous compounds a r e re$ponsible for much of t h e flavor of this mushroom. These were identified bv Murahashi in the 1930's a s methyl cinnamate 11) and m.&sutnke alcohol (11. I - 0 c t e n - 3 - o l J . ~Methyl ~' cinnamate is rrsponuible for t h e spicy smell t h a t is characteristic of this m&hroom, a n d matsutake alcohol has a "mushroom odor." T h e latter compound has been identified as major odor component of many edible mushroom^.^ This article describes t h e synthesis of methyl cinnamate as a n experiment for t h e undergraduate organic chemistry laboratory a n d t h e synthesis of 1octen-3-01 as a project for advanced students. Attempts t o prepare methyl cinnamate by acid-catalyzed esterification of cinnamic acid in excess methanol gave only low yields of the desired product. Treatment of cinnamic acid (111) with thionyl chloride t o form t h e acid chloride (IV) a n d reaction of this with methanol in t h e presence of polyvinylpyridine5 gave I in 77% yield.
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I -0cten-:%olwas prrpared by the reaction of pentylmagnriium l ~ r o m ~ dI Ve I w ~ t hacrolein rVI). 1)ue t o t h e fact that acrolein is a potent lachrymator, t h e Grignard reagent was used in excess so n o trace of i t appeared in t h e final product. Also, t h e lachrymatory nature of acrolein is t h e reason i t is not recommended for beginning students.
0
+
II
CH3CH2CH2CH2CH2MgBr CHz=CHCH v VI
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addedO.10 mol(7.25 mL) of SOClaand one drop of dimethylformamide. The reaction mixture was kept a t room temperature for 30 min with the escaping gases being vented to a trap. It was then refluxed for 15 min on a steamhath. The excess SOClz was then removed by distillation on a steambath with final traces being removed by the addition of 10 mL of hexanes to the flask and then their removal by distillation. This last step with the addition and removal of the hexanes was done a second time. Then 25 mL of dry CH2ClZwas added to the flask containing the acidchloride and themixture was swirleduntil theacid chloride had dissolved. Then 5.0 g of 4-polyvinylpyridine(ReillyTar and Chemical Co., R-8050) and 0.10 mol (4.1 mL) of methanol were added to the flask. On addition of the methanol the reaction mixture got hot and refluxed gently for shout 5 min. The mixture was then refluxed using a steambath for an additional 5 min. On cooling the reaction mixture was filtered to remove the solid 4-polyvinylpyridine.The 4polyvinylpyridine was washed three times with 10 ml of CHCB and the washings were added to the original CHzCll solution. The eomhined CH2C12solution was then washed with 25 mL of 5% NaHCOs and then dried with anhydrous CaC12. The CHZCIZwas removed from the product by distillation on a steamhath to give 6.2 g (77% yield) of agolden liquid that solidified on standing. The productwas essentially pure as a TLC analysis of the product showed only a single spot (silica gel with indicator using CHzCIz as eluting solvent); the NMR contained only the absorptions expected for the product (CClr, TMS internal standard), 6 = 3.7 (s, 3H), 6.9 (d, lH), 7.2-7.4 (multiplet, 5H), and 7.6 (d, 1H); and a m.p. of 34-35' (lit. m.p. = 36"). (RS~l-Octen-3-ol(II) Into a 500-mL three-necked round-bottomed flask fitted with a reflux condenser, an addition funnel and a stopper was introduced 0.20 mol of magnesium turnings, 25 mL of diethyl ether and a magnetic spin bar. A solution of 0.20 mol of l-bromopentane in 50 mL of diethylether was put into theaddition funneland about 1mL was added to the flask containing the magnesium. After the reaction had started (refluxing), additional l-hromopentane solution was added dropwise at arate to keep the stirred reactionmixture refluxing. After refluxing had ceased, the solution was stirred for an additional 15 min. An ice hath was then placed on the outside of the flask containing the stirred reaction mixture and 0.19 mol of acrolein (caution: lachrymator; make transfers in a fume hood) in 50 mL of diethyl ether was added dropwise (caution: exothermic reaction). Then 50 mL of 1.OM HCI was added to the reaction mixture and the ether layer was collected using a separatory funnel. The ether solution was dried with anhydrous CaC12, after which the ether was removed by distillation an a steam hath. The product was isolated by distillation as the fraction boiling between 168 and 178'; yield 24.4g (45%);IR (NaCI plates) 3375 cm-' (-OH stretch), 2945 and 2875 cm-I (-CH2-stretch), 1650 em-' (-C=C- stretch), 1470 em-' (-CH2-overtone), 995 and 920 em-') (-CH==CH2out of plane); NMR (CC4,TMS internalstandard) b = 0.90 (d, 3H), 1.35 (multiplet,8H), 5.0 (multiplet, 1H) 5.25 (d, lH), 5.75 (multiplet, 1H); and no2' = 1.4359 (lit. nr,% = 1.4361).
OH
' Armiilaria ponderosa is the species imported from the U.S.A.
trans-Methyl cinnamate (I) To 0.050 mol of einnamic acid in a 100-mLround-bottomed flask fitted with a reflux condenser and containing boiling chips was
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Murahashi. S.. Sci. Pap. Insf. Phys. Chem. Res. (Tokyo), 30, 263 (1936). (C.A., 31,3001') Murahashi, S., Sci. Pap. Inst. Phys. Chem. Res. (Tokyo), 34, 155 (1936). (C.A., 32,375SS) Maga, J. A., J. Agric. Foodchem., 29, I (1961). Getmann, D., Hagerty, D.,Wilson, G., and Wood. W. F., J. CHEM Eouc.. 61, 550 (1984).
