the nitrogen atom with different π-nucleophiles affords hydroxylactams 9-14 in good yields. The latter compounds are excellent precursors for the α-acyliminium ion 16 and can be stereoselectively cyclized in HCOOH to yield novel heterocyclic ring systems of varied structures. Because of the stereoelectronic control in the ring closure stereoselective syntheses, such as the conversion of 8a to 24, are
                                    在氮原子上被不同的π-亲核试剂取代的
噻唑烷二酮3-8的区域选择性NaBH 4 / H +还原以良好的产率提供羟基内酰胺9-14。后面的化合物是α-酰化
铵离子16的极好的前体,可以在HCOOH中进行立体选择环化,以产生具有不同结构的新型杂环系统。由于闭环中的立体电子控制,很容易实现立体选择性合成,例如8a到24的转换。