Regioselective C-O bond cleavage reactions of acetals

Reactions of acetonide derivatives of monosaccharides with the Grignard reagent in benzene afford the corresponding monosaccharide derivatives having only one free hydroxy group. 1,4-di-alkoxy-(2S,3S)-2,3-butanediols are obtained from the reactions of 2S,3S-threitol bisketals with Grignard reagents or with LiAlH4/AlCl3. The reactions of benzylic acetals prepared from 1,4-dialkoxy-(2S, 3S)-2,3-butanediols and aromatic aldehydes, with aryl or secondary or sterically hindered Grignard reagents give the corresponding ring-opening products in high diastereoselectivity. Other synthetic applications of such tunable chiral diols are briefly described.