Stereoselective total synthesis of (–)-pumiliotoxin C by an aqueous intramolecular acylnitroso Diels–Alder approach
作者:Masaichi Naruse、Sakae Aoyagi、Chihiro Kibayashi
DOI:10.1039/p19960001113
日期:——
A chiral approach to (–)-pumiliotoxin C based on an aqueous intramolecular acylnitroso Diels–Alder reaction is described. Upon treatment of the (S)-1,3-diene hydroxamic acid 19, available from L-malic acid, with Pr4NIO4 under the aqueous conditions, the in situ generated acylnitroso compound 19 was subjected to intramolecular [4 + 2] cycloaddition to yield the trans-1,2-oxazino lactam 21 with significantly
描述了一种基于水分子内酰基亚硝基Diels-Alder反应的(-)-pumiliotoxin C的手性方法。在水性条件下用Pr 4 NIO 4处理可从L-苹果酸得到的(S)-1,3-二烯异羟肟酸19 ,将原位生成的酰基亚硝基化合物19进行分子内[4 + 2]处理。与在氯仿溶液中进行的相同环加成相比,环加成生成反式-1,2-恶嗪内酰胺21的非对映选择性大大提高。随后通过串联格氏反应– NaBH 3添加丙基侧链以完全立体控制的方式减少CN。如此获得的双环1,2-恶嗪26通过顺序还原性N-O键裂解,二酮31的羟醛缩合和八氢喹诺酮33的氢化转化为全顺式-十氢喹啉34。Clemmensen还原为34,然后进行LiAlH 4还原,提供了一个ca。2:1的α-甲基和β-甲基异构体36和37的差向异构混合物,然后进行脱苄基作用,将主要异构体36转化为5- epi- pumiliotoxin C2。另一方面,对34个化合物进行了AlAlH