A new synthetic route to the antibiotics (+)-PS-5 and (+)-PS-6 is described. The preparation involves a fully stereocontrolled reaction between the enantiomerically pure N- trimethylsilylimine of lactic or mandelic aldehyde and the lithium enolate of the tert-butyl butanoate or tert-butyl isovalerate, respectively. Conversion of the azetidinones obtained to 4-acetoxy derivatives via oxidative cleavage of the hydroxyethyl or hydroxybenzyl side ...
![(5R,6R)-benzhydryl 3-[(2-acetamidoethyl)thio]-6-isopropyl-7-oxo-1-azabicyclo[3.2.0]hept-2-ene-2-carboxylate Structure](https://image.chemsrc.com/caspic/391/135560-72-4.png)
![(2R,5R,6R)-benzhydryl 6-isopropyl-3,7-dioxo-1-azabicyclo[3.2.0]heptane-2-carboxylate Structure](https://image.chemsrc.com/caspic/429/135560-71-3.png)