N-PENTENYL GLYCOSIDE METHODOLOGY IN THE STEREOSELECTIVE CONSTRUCTION OF THE TETRASACCHARYL CAP PORTION OF LEISHMANIA LIPOPHOSPHOGLYCAN

Efficient and high yielding stereoselective assembly of the tetrasacch aryl cap region of the lipophosphoglycan from the protozoan parasite L eishmania using the n-pentenyl glycoside protocol is described in this paper. Both convergent and linear syntheses lead to the protected tet rasaccharide 14; however, the convergent assembly is more efficient in terms of product recovery. Regioselective reductive cleavage of benzy lidene acetal 4 with triethylsilane-trifluoroacetic acid system libera tes the required C-4 OH in excellent yield, without affecting the resi dent chloroacetate functionality.