Highly stereoselective synthesis of enantiomerically pure B-hydroxy-gamma-sulfenyl-gamma-butyrolactone by asymmetric Pummerer type cyclization

Enantiomerically pure t-butyl 4-sulfinyl-3-silyloxy-butanoate can be transf ormed stereoselectively in a Pummerer reaction with TFAA into the usual ald ehyde or into a cis beta-hydroxy-gamma-sulfenyl-gamma-butyrolactone. Experi mental conditions allowing total control of the reaction in favor of either the aldehyde or the gamma-butyrolactone are described. The corresponding m ethyl butanoate led, under the same conditions, only to the aldehyde. (C) 2 000 Elsevier Science Ltd. All rights reserved.