Stereoselective 1,3-dipolar cycloadditions of thioketones to carbohydrate-derived nitrones

摘要

A series of cycloaliphatic thioketones was reacted with selected enantiopure nitrones bearing carbohydrate-derived moieties leading to 1,4,2-oxathiazolidine derivatives in a highly stereoselective manner. Analysis of spectroscopic data supplemented by X-ray diffraction analysis of the major products confirmed the anti-configuration in the series derived from D-glyceraldehyde and L-erythrose-functionalized nitrones bearing a sugar moiety at the C atom. In the case of the model benzaldehyde-derived nitrone decorated at the N atom with carbohydrate auxiliary, and also for a L-erythrose-derived cyclic nitrone, in the reaction with sterically crowded 2,2,4,4-tetramethyl-3-thioxocyclobutanone the exclusive formation of single diastereoisomeric products was observed indicating an excellent steric match of the substrates. Dissociation constants of selected (3+2)-cycloadducts were determined by H-1 NMR spectroscopy. (C) 2016 Elsevier Ltd. All rights reserved.