Conjugate addition of 6-membered hydrazine to chiral tert-butyl (E)-2-(p-tolylsulfinyl)cinnamates. Synthesis of (S)-celacinnine
作者:Haruo Matsuyama、Nobuhiro Itoh、Aoi Matsumoto、Nahoko Ohira、Kenji Hara、Masato Yoshida、Masahiko Iyoda
DOI:10.1039/b107443c
日期:2001.11.15
Two enantiomers of the bicyclic lactam, (S)- and (R)-9-phenyl-1,6-diazabicyclo[4.3.0]nonan-7-one (6), were synthesized stereoselectively with high optical purity (95% ee) by the asymmetric conjugate addition–cyclization of piperidazine to chiral vinyl sulfoxides, tert-butyl (E)-2-[(R)- and (S)-p-tolylsulfinyl]cinnamate (4), followed by removal of the p-tolylsulfinyl group with SmI2. The subsequent reductive cleavage of the N–N bond of the bicyclic lactam 6 with sodium in liquid ammonia produced the corresponding 9-membered azalactam, (S)- and (R)-4-phenyl-1,5-diazacyclononan-2-one (7) with 99% and 97% ee, respectively. X-Ray crystallography showed that (S)-7 exists exclusively as a trans conformer in the crystal state. Starting from (S)-7, naturally occurring (S)-celacinnine 1 was synthesized with 99% ee employing the ring-expansion reaction via intramolecular transamidation.
双环内酰胺的两个对映体,(S)-和(R)-9-苯基-1,6-二氮杂双环[4.3.0]壬烷-7-酮(6),通过手性乙烯基亚砜与哌啶嗪的不对称共轭加成-环化反应,后进行SmI2去对甲苯亚砜基,以高光学纯度(95% ee)进行立体选择性合成。随后,通过在液氨中使用钠对双环内酰胺6的N–N键进行还原裂解,分别得到相应的9元氮内酰胺,(S)-和(R)-4-苯基-1,5-二氮杂环壬烷-2-酮(7),其光学纯度分别为99%和97% ee。X射线晶体学显示,(S)-7在晶态下仅以trans构象存在。以(S)-7为起始物,通过环扩张反应经分子内转氨反应合成了天然存在的(S)-celacinnine 1,其光学纯度为99% ee。