Synthesis of diastereo- and enantiomerically pure anti-3-methyl-1,4-pentanediol via lipase catalysed acylation

摘要

Racemic trans-4,5-dimethylhydrofuran-2(3H)-one was synthesised from 5-methyl-furan-2(3H)-one, (alpha-angelica lactone). The key reaction in the synthesis was the 1,4-conjugate addition of an organocuprate to 5-methylfuran-2(5H)-one (beta-angelica lactone). Different types of organocuprates were tested with the highest anti:syn ratio of 99.4:0.6 being obtained by the use of a Gilman organocuprate reagent. The enantioselective acylation of racemic 3-methyl-pentan-1,4-diol, catalysed by a variety of lipases in organic media, was investigated. The highest enantioselectivity (E > 400) was obtained when Novozyme 435 was used as the catalyst at a water activity of a(w) similar to 0. Thus, both enantiomers, (3S,4R)- and (3R,4S)-3-methyl-pentan-1,4-diol, were obtained in very high diastereomeric (> 99% de) and enantiomeric purities (> 99.8% and > 97.4% ee, respectively). (c) 2005 Elsevier Ltd. All rights reserved.