Stereoselective synthesis of C-glycosides by addition of titanium enolates from a chiral N-glycolyl thiazolidinethione to glycals

The Lewis acid-mediated addition of the titanium enolate from the pivaloyl-protected (S) N-glycolyl-4-isopropyl-1,3-thiazolidine-2-thione to glycals affords the corresponding syn C-α-glycosides in high yields and excellent diastereomeric ratios. Further removal of the chiral auxiliary permits access to enantiomerically pure C1′-pivaloyloxy pyrans in a straightforward manner.