Synthesis of N ‐(Glucopyranosid‐3‐yl)‐ D ‐ and ‐ L ‐alanyl‐ D ‐isoglutamine and Related Glycodipeptides

Six glucodipeptides, in which the D ‐lactyl‐ L ‐alanyl residue of the immunoadjuvant myramyl dipeptide is replaced by D ‐Ala, L ‐Ala, and Gly, have been synthesized. Coupling of benzyl 2‐acetamido‐4,6‐O‐benzylidene‐3‐[ R ‐(1‐carboxyethyl)amino‐, ‐ S ‐(1‐carboxyethyl)amino‐, and ‐(carboxymethyl)amino]‐2,3‐dideoxy‐α‐ D ‐glucopyranosides 8,9 , and 10 , respectively, with D ‐isoglutamine methyl ester and D ‐glutamine methyl ester followed by hydrogenolysis afforded the corresponding N ‐(2‐acetamido‐2,3‐dideoxy‐ D ‐glucopyranosid‐3‐yl) derivatives of D ‐Ala‐ D ‐isoGln‐OMe ( 14 ), L ‐Ala‐ D ‐isoGln‐OMe ( 15 ), Gly‐ D ‐isoGln‐OMe ( 16 ), D ‐Ala‐ D ‐Gln‐OMe ( 20 ), L ‐Ala‐ D ‐Gln‐OMe ( 21 ), and Gly‐ D ‐OMe ( 22 ).