Stereospecific and stereoselective syntheses of cis-12, and stereoselective synthesis of (±)-trans-12 from D-allo threonine and trans-crotonic acid, respectively, are described. The key steps in the syntheses are the formation of the β-lactam ring (4) by cyclization of the amide (3) via a complete Sn2 mechanism and stereocontrolled conversion of the azetidinone (4) to 12, 13 and 14, which are intermediates
立体特异性和立体选择性合成顺- 12,和(±)立体选择性合成-反式- 12从d-异体苏氨酸和反式-巴豆酸,分别进行说明。合成的关键步骤是通过酰胺(3)的S n 2完全作用机理将酰胺(3)环化,以及将氮杂环丁酮(4)立体转化为12、13和14,从而形成β-内酰胺环(4)。是青霉菌和碳青霉烯的中间体。