Highly Stereoselective 1,4-Conjugate Addition of Organocopper Reagents to Methyl α-<scp>d</scp>-Glucopyranoside Derivatives Tethering an Unsaturated Ester Moiety at C-4 or C-6<sup>1</sup>
[GRAPHICS]The 1,4-conjugate additions of a variety of organocopper reagents to some 4-O-crotonyl derivatives of methyl alpha-D-glucopyranoside proceeded with a high level of diastereochemical induction to provide the adducts carrying a beta-substituted butanoic ester at C-4, The 1,4-conjugate addition to a 6-O-crotonyl derivative afforded the adduct with reverse configuration at the beta-carbon to that obtained from the 4-O-crotonyl derivatives.
Highly Diastereoselective 1,4-Addition of an Organocuprate to Methyl α-<scp>d</scp>-Gluco-, α-<scp>d</scp>-Manno-, or α-<scp>d</scp>-Galactopyranosides Tethering an α,β-Unsaturated Ester. Novel Asymmetric Access to β-C-Substituted Butanoic Acids
yields. Other organocuprates also serve as effective carbon nucleophiles for the 1,4-addition. Removal of the carbohydrate moiety from each adduct afforded a variety of beta-C-substituted butanoic esters in remarkable enantiomeric excess. The 1,4-addition of the same cuprate to some methyl alpha-D-manno- or alpha-D-galactopyranosidic substrates in which a crotonyl group was incorporated, each at 3-OH