Partially benzylated oxazoline derivatives of 2-acetamido-2-deoxy-D-glucopyranose as “standardized intermediates” for oligosaccharide synthesis. preparation of disaccharides having the sequences β-D-GlcpNAc(1→x)-D-Gal and β-D-GlcpNAc(1→4)-D-GlcNAc

Abstract Three benzyl tri- O -benzyl-l-thio-β- D -galactopyranosides ( 5, 6 , and 7 ) were prepared from the corresponding O -acyltri- O -benzyl- D -galactopyranosyl bromides ( 1a-c ) via the benzylxanthates 2a-c and the fully protected benzyl thiogalactosides 3a-c . The α anomer ( 4 ) of 5 resulted from the reaction of bromide 1a with α-toluenethiol. Conditions were found for the successful coupling of O -acetyl-di- O -benzyl derivatives ( 8 and 13 ) of 2-methyl-(1,2-dideoxy-α- D -glucopyrano)-[2,1- d ]-2-oxazoline to the thiogalactosides 5-7, and to a partially protected glycoside ( 16 ) or 2-acetamido-2-deoxy- D -glucose. The products were fully substituted disaccharides of 2-acetamido-2-deoxy-β- D -glucose linked 1→3 ( 9a ), 1→6 ( 11a ), 1→4 ( 14a ), and 1→4 ( 17a ), respectively. Cleavage of the single, temporary protecting group ( O -acetyl) from these compounds gave partially deblocked disaccharides capable of chain extension from position 3′ ( 9b and 11b ) or 4′ ( 14b and 17b ).