Synthesis of 1-oxacephems from D-arabinal and L-rhamnal

Article abstract of DOI:10.1016/S0040-4020(97)00917-4

Readily available from D-arabinal and L-rhamnal 2-C:1-N-carbonyl-2-deoxy-β-D-arabino-and -α-L-gluco-pyranosylamines 5, 25 and 26 were transformed into cephems 45 and 49 via a sequence of reactions consisting of alkylation of the B-lactam nitrogen atom, deprotection of pyranoid hydroxy groups, glycolic cleavage of the vic diol grouping, discrimination of carbon atoms which were separated by periodate oxidation, and formation of the 1,3-oxazine six-membered ring fused to the p-lactam fragment. Discrimination of two aldehyde groups obtained during the glycolic cleavage step was achieved after their reduction and protection of one of the hydroxymethyl group by a bulky silyl substituent or by lactonization.