Synthesis of New Aza‐ C ‐disaccharides Linking 4‐Deoxy‐4‐amino‐β‐ L ‐ erythro ‐furanose to C‐2 of D ‐Glucose and D ‐Allose

The cross‐aldol condensation of N ‐benzyl‐2,5‐dideoxy‐2,5‐imino‐3,4‐ O ‐isopropylidene‐ L ‐ribose with 4,6‐ O ‐benzylidene‐2‐deoxy‐α‐ D ‐ erythro ‐hexopyranosid‐3‐ulose (potassium enolate + HMPA) gave an aldol as the major product. DAST‐induced water elimination gave two enones that were converted into the aza‐ C ‐disaccharides (+)‐ 4 [methyl 2‐deoxy‐2‐(1,2,5‐trideoxy‐2,5‐imino‐ L ‐ribitol‐1 C ‐yl)‐α‐ D ‐glucopyranoside] and (+)‐ 5 (the α‐ D ‐allopyranoside analogue). Reduction of the aldol and deprotection provided aza‐ C ‐disaccharide (+)‐ 3 {methyl 2‐deoxy‐2‐[(1 R or 1 S )‐2,5‐dideoxy‐2,5‐imino‐ L ‐ribitol‐1 C ‐yl]‐α‐ D ‐allopyranoside} with a hydroxymethano linker. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)