6α-bromo-6β-1(R)-hydroxyethylpenicillanate 、
Carbamic acid chlorocarbonylmethyl ester 在
tetrametylguanidine 作用下,
生成 2-[(2R,3S)-3-Bromo-2-(2-carbamoyloxy-acetylsulfanyl)-3-((R)-1-hydroxy-ethyl)-4-oxo-azetidin-1-yl]-3-methyl-but-2-enoic acid acetoxymethyl ester