(3S,4R)-3-(trimethylsilyl)-4-(phenylsulfonyl)-2-azetidinone
(3S,4R)-3-(trimethylsilyl)-4-(benzoylthio)-2-azetidinone
(3S,4R)-3-(trimethylsilyl)-4-phenoxy-2-azetidinone
(3S,4R)-3-(trimethylsilyl)-4-(phenylthio)-2-azetidinone
(4R)-4-phenylthio-2-azetidinone