Enantioselective transesterification of (RS)-1-chloro-3-(3,4-difluorophenoxy)-2-propanol using Pseudomonas aeruginosa lipases
作者:Manpreet Singh、Uttam Chand Banerjee
DOI:10.1016/j.tetasy.2007.08.024
日期:2007.9
Lipases from the bacterial strain, Pseudomonas aeruginosa, isolated from the soil by enrichment techniques, are assessed for the enantioselective transesterification of (RS)-1-chloro-3-(3,4-difluorophenoxy)-2-propanol (rac-CDPP) to (R)-1-chloro-3-(3,4-difluorophenoxy)-2-propanol, a key intermediate in the synthesis of the chiral drug (S)-Lubeluzole. The lipases produced by the organism yielded the (S)-ester and the (R)-alcohol as the remaining substrate with an excellent yield (>49.9%) and almost complete enantioselectivity (ee >99.9%) in the presence of vinyl butyrate as an acyl donor in an organic medium. In contrast, purified and expensive commercially available lipases of Candida rugosa and porcine pancreas achieved much lower conversion with en antioselectivities of 15% and 5%, respectively. A well-mixed (similar to 1000 rev min(-1)) batch reactor having the aqueous phase finally dispersed in hexane was used in these studies. The parameters of the transesterification reaction were optimized and the optimal concentrations of rac-CDPP and vinyl butyrate were found to be 5 and 150 mM at 30 degrees C. A preparative-scale reaction yielded the (S)-ester at 42% conversion and ee >99%. (C) 2007 Elsevier Ltd. All rights reserved.