Stereoselective carbon-carbon bond forming reactions of chiral cyclopent-2-enone and cyclopentene-1-methanol, both spiro-connecting a 1,2 : 5,6-di-O-isopropylidene-alpha-D-glucofuranosyl ring

The conjugate additions of a variety of organocopper reagents or dimethyl m alonate anion to a spirocyclic cyclopent-2-enone connecting a 1,2:5,6-di-O- isopropylidene-alpha-D-glucofuranosyl ring as a constituent of the spiro st ructure, namely ( 1S,3R,4R,5R)-3,4-(isopropylidenedioxy)-1-[(1R)-1,2-(isopr opylidenedioxy)ethyl]-2-oxaspiro[4.4]non-6-en-8-one, proceeded stereoselect ively in some cases affording a variety of beta-functionalized cyclopentano ne derivatives. The thermal treatment of (1S,3R,4R,5R)-7-(hydroxymethyl)-3, 4-(isopropylidenedioxy)-1-[(1R)-1,2-(isopropylidenedioxy)ethyl]-2-oxaspiro[ 4.4]non-6-ene, another D-glucose-derived spirocyclic substrate, with trieth yl orthoacetate in the presence of a catalytic amount of acid afforded the Claisen rearrangement product with a high level of diastereoselectivity. (C ) 2000 Elsevier Science Ltd. All rights reserved.