Enantioselective synthesis of loracarbef from sodium erythorbate

Article abstract of DOI:10.1016/S0040-4039(00)91559-4

Sodium erythorbate (7) has been converted to loracarbef (1). Oxidation of sodium erythorbate to D erythronolactone (8) followed by selective monotosylation and treatment with sodium ethoxide provided ethyl (2S,3R) 4 hydroxy 2.3 epoxybutyrate (10). Swern oxidation of this epoxide into the aldehyde (11), imine formation with tert-butylglycinate and an enantioselective Staudinger reaction with phthalimidoacetyl chloride afforded the (3S,4S)-cis-β-lactam (13). Appropriate functional group manipulations followed by a Dieckmann condensation, chlorination, and protecting group removals gave the enantiomerically pure nucleus of loracarbef (24).