Acetal formation by solvolysis of glucal-derived donor–acceptor cyclopropanes

The conversion of glucal derived donor–acceptor cyclopropanes to acetals by TiCl4 mediated ring opening and alcohol trapping is described. Good selectivity for the alpha anomer and yields near 90% are consistently observed with aliphatic, benzylic and allylic alcohols, phenols and thiophenols. The utility of this method to prepare oligosaccharides through intermediate O,S-acetals is illustrated.