The deprotonation of 3-substituted-furan-2(5H)-ones 1, obtained via the hydrolysis of 3-substituted-2,5-dihydro-2,5-dimethoxyfurans, affords in the reaction with both aromatic and aliphatic aldehydes regioselectively the unsaturated 3-substituted 5-(1′-hydroxy)-γ-butyrolactones, such as 4, 5, 6, 7, 8, 9 and 10. The use of Lewis acids allows modulation of the diastereoisomeric ratios. The subsequent
Reactions of 2,5-dihydro-2,5-dimethoxy-furan with phenylselenenylchloride: Regio- and stereocontrolled generation of highly functionalized C4 building-blocks
An efficient protocol for stereo- and regiocontrolledsynthesis of small polyfunctional molecules is presented. The stereospecific addition of PhSeCl to 2,5-dihydro-2,5-dimethoxy-furan 1 in solvents, such as methylene chloride and methanol, gives cyclic and linear acetals 2 and 3, depending on the solvent used. Emphasis is given to the regiocontrolled hydrolysis of acetal groups for the preparation
Deprotonation of N-benzyl-3-phenylselenylpyrrol-2(5H)-one 3 and furan-2(5H)-one 4 and reaction with aldehydes affords regioselectively 5-(1'-hydroxy)-gamma-butyrolactones and the aza-analogous butyrolactams with good diastereoisomeric excesses. The presence of Lewis acids enhances the diastereoisomeric ratios.This methodology is an alternative to Lewis acid mediated silyloxydiene condensation. (C) 2000 Elsevier Science Ltd. All rights reserved.