Convenient double-enzymatic synthesis of both enantiomers of 6-methyl-ε-caprolactone

Both enantiomers of 6-methyl-ε-caprolactone (6-MeCL) are obtained in high enantiomeric excess by the combination of an enzymatic ring opening of racemic 6-methyl-ε-caprolactone and subsequent enzymatic ring closure. Immobilized Candida antarctica lipase B (Novozym 435) was selected as the biocatalyst for both the ring-opening and the ring-closing reaction. This route provides ready access to enantiopure (S)-6-MeCL (ee = 99.6%) and (R)-6-MeCL (ee = 98.8%).