Novel azetidinones for carbapenems and fragmentation in the allylamine precursor analogue

(2R,3R)-N-(3-Methoxy-2,3-dioxopropyl)-N-(4-methoxy-phenyl)-2,3-epoxybutanamide on treatment with strong bases (LDA, LHMDS) gives 3-[(1R)-1-hydroxyethyl]azetidin-2-one derivative, while the N-(3-methoxy-2-methylidene-3-oxo-propyl) analogue undergoes fragmentation.