4-O-Benzyl-23-O-isopropylidene-L-threose: A useful building block for stereoselective synthesis of monosaccharides

4-O-Benzyl-23-O-isopropylidene-L-threose readily available from L-tartaric acid is a quite useful four-carbon building block for monosaccharide synthesis. The versatility can be reinforced by the coupled use of stereoselective addition reactions where the suitable choice of organometallics leads to highly anti-selective additions. The building block is particularly useful in the synthesis of rare sugars the versatility of which is demonstrated by the synthesis of some L-sugars as well as the formal total synthesis of polyoxin J in convergent manner.