Abstract A stereoselective chemoenzymatic synthesis of all four stereoisomers of tert-butyl 6- chloro-3, 5-dihydroxy-hexanoate (6 a) is presented. The key step of the sequence is a highly regio-and enantioselective single-site reduction of tert-butyl 6-chloro-3, 5-dioxohexanoate (1 a) by two enantiocomplementary biocatalysts. Alcohol dehydrogenase from Lactobacillus brevis (recLBADH) afforded a 72% yield of enantiopure tert-butyl (S)-6-chloro-5-hydroxy-3 ...