hydrogenation of racemic 5 using ruthenium-BINAP-diamine-KOH system, followed by oxidation. Magnesium enolate of (2S)-2-methoxycyclohexanone [(S)-5] reacts with the 4-acetoxyazetidinone 4 to give the key intermediate 3 with high yield and diastereoselectivity for the synthesis of sanfetrinem 1.
Both stereospecific and stereoselective syntheses of thienamycin intermediates which have the correct configurations at the three contiguous chiral centers are reported.