The enzymatic lactonization of three acyclic gamma,delta-epoxy esters (ethyl 3,7-dimethyl-4,5-epoxyoctanoate, ethyl 3,7,7-trimethyl-4,5-epoxyoctanoate, and ethyl 3,3,7-trimethyl-4,5-epoxyoctanoate) by apple fruit (Malus silvestris) and Jerusalem artichoke bulb (Helianthus tuberosus L.) was investigated. The substrates were transformed into a mixture of isomeric delta-hydroxy-gamma-lactones and gamma-hydroxy-delta-lactones. The gamma-lactones (yields ranging from 45-70%) predominated over delta-lactones (yields ranging from 8-40%). The composition of the product mixture depended on the structure of substrate as well as the biocatalyst. The enzymatic system in these biocatalysts also exhibited diastereoselectivity and enantio selectivity. (C) 2003 Elsevier Science (USA). All rights reserved.