1,4-Dithiothreitol mediated cleavage of the acetal and ketal type of diol protecting groups

The use of 1,4-dithiothreitol (DTT) as an acetal or ketal exchange reagent and camphorsulfonic acid (CSA) as a catalyst permitted the efficient removal of benzylidene acetal and isopropylidene ketal protecting groups under mild conditions. A variety of acetal and ketal protected carbohydrates were deprotected with this method in 78–98% yields. In addition, terminal isopropylidene ketal or benzylidene acetal was selectively cleaved in the presence of internal isopropylidene ketal. Moreover, it was found that an unusual seven-membered 1,3-dithiepane was formed during the deprotection of benzylidene acetal with DTT.