SYNTHESIS OF LIGANDS RELATED TO THE VIBRIO-CHOLERAE O-SPECIFIC ANTIGEN .2. IMPROVED SYNTHESIS AND THE CRYSTAL-STRUCTURE OF METHYL 4,6-DIDEOXY-4-(3-DEOXY-L-GLYCERO-TETRONAMIDO)-ALPHA-D-MANNOPYRANOSIDE, THE METHYL ALPHA-GLYCOSIDE OF THE INTRACATENARY REPEATING UNIT OF THE O-POLYSACCHARIDE OF VIBRIO-CHOLERAE O/1

The crude product of deamination of the commercially available L-homoserine was acetylated and the 2-O-acetyl-3-deoxy-L-glycero-tetronolactone (18) formed was used to N-acylate methyl perosaminide (methyl 4-amino-4,6-dideoxy-alpha-D-mannopyranoside, 12) and its 2,3-O-isopropylidene derivative. The major product isolated from the reaction was the crystalline methyl 4-(4-O-acetyl-3-deoxy-L-glycero-tetronamido)-4,6-dideoxy-alpha-D-manno-pyranoside (1, 70-75%) resulting from acetyl group migration in the initially formed 2'-O-acetyl derivative. O-Deacetylation of 1 gave the title amide 2. Compound 2, obtained crystalline for the first time, was fully characterized, and its crystal structure was determined. Deoxytetronamido derivatives diastereomeric with 1 and 2, respectively, were obtained by the acylation of 12 with 2-O-acetyl-3-deoxy-D-glycero-tetronolactone (prepared from D-homoserine), and subsequent deacetylation. Structures of several byproducts of the reaction of 12 with 18 have been deduced from their spectral characteristics. Since these byproducts were various O-acetyl derivatives of 2, the title compound could be obtained in similar to 90% yield by deacetylating (Zemplen) the crude mixture of N-acylation products, followed by chromatography.