trans-3-Methyl-4-octanolide, also called trans-β-methyl-γ-octalactone is a chemical compound of the lactone family with formula . It exists in two stereoisomers: (3R,4S) and (3S,4R).
The (3S,4R) form is found in whiskey and other alcoholic beverages that have been aged in oak barrels, together with the more important cis isomer.Hans-Dieter Belitz, Peter Schieberle, and Werner Grosch (2004) Food Chemistry, page 383. Springer, It has a coconut, celery or fresh wood aroma, that can be detected by humans at the concentration of 20 μg/L in air.Eric Masson, Raymond Baumes, Christine Le Guernevé, and Jean-Louis Puech (2000) Identification of a Precursor of β-Methyl-γ-octalactone in the Wood of Sessile Oak (Quercus petraea (Matt.) Liebl.). J. Agric. Food Chem. volume 48, pages 4306-4309 A mixture of the cis and trans isomers is repellent for mosquitos and flies.Yukio Suzuki, Wakako Mori, Hiroyuki Ishizone, Koichi Naito, and Toshio Honda (1992) Concise Enantiospecific Syntheses of (+)-Eldanolide and (−)-cis-Whisky Lactone. Tetrahedron letters, volume 33, pages 4931-4932
The (3S,4R) isomer is extracted by the alcoholic beverage from some precursor substances in the oak wood.Masuda and Nishimura (1971), Branched nonalactones from some Quercus species. Phytochemistry, volume 10, pages 1401-1402. It can be synthesized in various ways.Hisashi Nishikori, Katsuji Ito, and Tsutomu Katsuki (1998) A short-step synthesis of trans-whisky lactone by an asymmetric Michael reaction. Tetrahedron: Asymmetry, volume 9, pages 1165–1170.Katsuji Ito, Miwa Yoshitake and Tsutomu Katsuki (1995), Enantioselective Synthesis of trans-Whisky Lactone by Using Newly Developed Asymmetric Ring Expansion Reaction of Oxetane as a Key Step. Chemistry Letters, volume 24, issue 11, page 1027
See also cis-3-Methyl-4-octanolide, the more important stereoisomer
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