(3R,4R)-4-((R)-1-Hydroxy-but-3-enyl)-3-methoxy-1-(4-methoxy-phenyl)-azetidin-2-one 、 alkaline earth salt of/the/ methylsulfuric acid 以88%的产率得到(R)-Acetoxy-phenyl-acetic acid (R)-1-[(2R,3R)-3-methoxy-1-(4-methoxy-phenyl)-4-oxo-azetidin-2-yl]-but-3-enyl ester