Formation of β-lactams fused to the pyranoid ring via the Mitsunobu reaction

N-Tosyl-2-C-carbamoyl glycosides having the α-l-arabino- and β-d-xylo- configuration form under Mitsunobu conditions 2-C:3-N-carbonyl-2,3-dideoxy-3-N-tosylamino-α-l-lyxo- and β-d-arabinopyranosides, respectively, having the β-lactam ring fused to the pyranoid one; neither the formation of the γ-lactam ring nor that of the 3,4-epoxide were observed. The γ-lactam 2-C:4-N-carbonyl-2,4-dideoxy-4-N-tosylamino-β-d-xylopyranoside can be obtained after protection of the 3-hydroxy group in the starting glycoside of α-l-arabino-configuration. The structure and configuration of methyl 2-C:3-N-carbonyl-2,3-dideoxy-3-N-tosylamino-β-d-ribopyranoside and methyl 2-C:3-N-carbonyl-2,3-dideoxy-3-N-tosylamino-β-d-erythro-pyranosid-4-ulose were proved by X-ray crystallography.