“…It is noteworthy that the C -1 benzyl ester of Neu5Ac gave a higher α-selectivity than those protected as a methyl ester . Other sialyl phosphites −O( n -Bu), −OCH 2 CH 2 Cl, −OCH 2 CCl 3 , −O(CH 2 ) 3 O-, O−CH 2 CH 2 Me 2 CH 2 O-, and 1,2- O -cyclopentyl were found to be less efficient than their OEt or OBn counterparts. However, dimethyl phosphite proved to be rather reactive, especially when promoted with ZnCl 2 /AgClO 4 in CH 2 Cl 2 at room temperature, providing sialosides in high yields (83−85%) and good β-stereoselectivity (α/β 1/5−6) when performed with simple acceptors.…”