Isoxazolidin-5-one analogs of β-lactam antibiotics

Isoxazolidin-5-ones, readily available via conjugate addition–rearrangement of hydroxylamine to α,β-unsaturated sugar 1,5-lactones, react with aldehydes and diethoxymethyl acetate to afford 2,4,5-trisubstituted 1-aza-3,9-dioxa-8-oxo-bicyclo[4.3.0]nonanes. 4,5-Disubstituted 1-aza-2-butoxycarbonyl-3,9-dioxa-8-oxo-bicyclo[4.3.0]nonanes undergo base-catalyzed rearrangement to 4,6-disubstituted butyl 2,3-dideoxy-3-N-oxamate-d-ribohexaldono-1,5-lactones. The configuration of representative compounds: (2S,4R,5S,6S) 5-acetoxy-4-acetoxymethyl-1-aza-3,9-dioxo-2-methyl-8-oxo-bicyclo[4.3.0]nonane and butyl 4,6-di-O-(tert-butyldimethylsilyl)-2,3-dideoxy-3-N-oxamate-d-ribohexaldono-1,5-lactone were proved by X-ray crystallography.