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报道手性合成砌块(4S,5R)-N-苄基-4-苄氧基-5-羟甲基-2-吡咯烷酮(3a)的直接还原氰基化及产物的立体化学与转化研究.含未保护羟基的内酰胺用Li Al H4/KCN体系直接还原氰基化,生成比例为69∶31的2,5-反式/顺式非对映立体异构体.与文献类似结果对比显示,氰基负离子对5-羟甲基-(35)-1-吡咯啉鎓中间体的加成主要受立体电子效应和C(5)位取代基(羟甲基)与进攻试剂间烯丙型1,3-位阻控制.该混合物在碱性条件下水解,生成比例为10∶90的2,5-反式/2,5-顺式-bulgecinine衍生物.这一结果表明氰基水解反应伴随着在C(2)位发生了有合成价值的串联差向异构化.由此建立了立体选择性地合成2,5-顺式(-)-N-甲基-2-别-bulgecinine的简便方法.
The direct reductive cyclization of the chiral building block (4S, 5R) -N-benzyl-4-benzyloxy-5-hydroxymethyl-2-pyrrolidone (3a) and the stereochemistry and transformation of the product were reported. Lactams containing unprotected hydroxyl groups were directly reductively cyanidated with a Li Al H4 / KCN system to give 2,5-trans / cis diastereoisomers in a ratio of 69:31. A comparison of similar results with the literature , The addition of cyano anions to 5-hydroxymethyl- (35) -1-pyrrolinium onium intermediates is mainly affected by the stereoelectronic effect and the C (5) substituent (hydroxymethyl) 1,3-H Blocking The mixture was hydrolyzed under basic conditions to give 2,5-trans / 2,5-cis-bulgecinine derivatives in a ratio of 10:90 This result shows that the cyanohydrolysis reaction Accompanied by the occurrence of a series of epimerization with synthetic value at the C (2) position, thereby establishing a stereoselective synthesis of 2,5-cis-N-methyl-2-bis-bulgecinine Easy way.