C12-monosaccharide derivative 2 (obtained from C12-dialdose 1 in 49% overall yield) was used as the starting material for the preparation of C19- and C21-monosaccharide derivatives. Coupling of aldehyde 3 (prepared from the parent alcohol 2) with the sugar derived phosphonates 8, 9, and 10 afforded the C21- (11 and 12 respectively) and C19- (13) monosaccharide derivatives. Aldehyde 3 reacted with phosphorane