n-Pentenyl Glycoside Methodology in the Stereoselective Construction of the Tetrasaccharyl Cap Portion of Leishmania Lipophosphoglycan

Efficient and high yielding stereoselective assembly of the tetrasaccharyl cap region of the lipophosphoglycan from the protozoan parasite Leishmania using the n -pentenyl glycoside protocol is described in this paper. Both convergent and linear syntheses lead to the protected tetrasaccharide 14; however, the convergent assembly is more efficient in terms of product recovery. Regioselective reductive cleavage of benzylidene acetal 4 with triethylsilane−trifluoroacetic acid system liberates the required C-4 OH in excellent yield, without affecting the resident chloroacetate functionality.