The 4-chloroazetidinone 10, a very reactive chiral intermediate for 1-β-methylcarbapenems (1b), was easily prepared and isolated as a solid crystalline compound from the corresponding sulfide 5. Another chiral intermediate (16d) bearing the 1-β-methyl moiety was prepared by stereoselective aldol type condensation of either azetidinone 4 or 10 with metal enolates 14 (R = S—Bu′, M = ZrCp2Cl, [Formula: see text], and SnBr). The β/α ratios were 9:1, 3:1, 2:1 respectively.
4-氯吡嗪酮10是1-β-甲基卡巴比林(1b)的非常活性手性中间体,可以从相应的硫醚5中轻松制备并分离为固体结晶化合物。另一个携带1-β-甲基基团的手性中间体(16d)是通过对吡嗪酮4或10与金属烯醇酸盐14(R = S—Bu',M = ZrCp2Cl,[Formula: see text]和SnBr)的立体选择性醛缩反应制备的。β/α比例分别为9:1,3:1,2:1。