steps and 30 % overall yield. Thus, (S)-3-benzyloxy-2-methylpropanal readily obtainable from (S)-5, was condensed with di-p-anisylmethylamine to afford the chiral imine. The [2+2]-cycloaddition reaction of diketene with the imine was found to proceed in a highly diastereoselective manner, giving the desired 3,4-trans-3-acetyl-β-lactam (max. diastereoselectivity 11-15:1). This was readily elaborated to
由(S)-3-羟基-
2-甲基-
丙酸甲酯((S)-5)分十步有效地合成了1β-
甲基咔啉的关键
中间体(2),总收率为30%。因此,将可容易地从(S)-5获得的(S)-3-苄
氧基-
2-甲基丙醛与
二对茴香基
甲胺缩合,得到手性
亚胺。发现
双烯酮与
亚胺的[2 + 2]-环加成反应以高度非对映选择性的方式进行,得到所需的3,4-反式-3-
乙酰基-β-内
酰胺(最大非对映选择性为11-15:1)。 。通过五个连续的操作可以很容易地将其详细说明为2。