Efficient and flexible syntheses of 1,4-disubstituted quinolizidine-type poison-frog alkaloids using the highlystereoselective Michael-type conjugate addition reaction as the key step are described. The 1,4-disubstituted quinolizidine poison-frog alkaloids 233A, 235U and 251AA are reported.
Flexible Syntheses of 5,8-Disubstituted Indolizidine Poisonous-Frog Alkaloids via a Michael-Type Conjugate Addition
作者:De-Jun Zhou、Zhen-Hui Wang、Yan-Ru Zhang、Zheng-Guo Cui
DOI:10.3184/174751917x14858862342223
日期:2017.2
The efficient and flexible syntheses of 5,8-disubstituted indolizidine poisonous-frog alkaloids is described using a highlystereoselective Michael-type conjugate addition reaction as the key step. In this work, syntheses of the 5,8-disubstituted indolizidine poisonous-frog alkaloids (–)-231C, (–)-221I and the proposed structure for (–)-193E are reported.
The enantioselective synthesis of poison-frog alkaloids (−)-203A, (−)-209B, (−)-231C, (−)-233D, and (−)-235B″
作者:Naoki Toyooka、Zhou Dejun、Hideo Nemoto、H. Martin Garraffo、Thomas F. Spande、John W. Daly
DOI:10.1016/j.tetlet.2005.11.047
日期:2006.1
The enantioselective synthesis of indolizidines (−)-203A, (−)-209B, (−)-231C, (−)-233D, and (−)-235B″ has been achieved and the absolute stereochemistry of both indolizidines 203A and 233D was established as 5S,8R,9S. The relative stereochemistry of natural 231C was established by the present asymmetric synthesis.
(â)-Kaitocephalin has been synthesized. With the C9 stereocenter from Garner's aldehyde, the C4 quaternary carbon was installed by the desymmetrization of the Cbz-protected serinol. The remaining stereogenic centers were generated through mercuriocyclization, epoxidation and regioselective epoxide opening, in which the quaternary carbon most likely played crucial roles in the stereoinduction.
Enantioselective syntheses of poison-frog alkaloids: 219F and 221I and an epimer of 193E
作者:Naoki Toyooka、Zhou Dejun、Hideo Nemoto、H. Martin Garraffo、Thomas F. Spande、John W. Daly
DOI:10.1016/j.tetlet.2005.11.046
日期:2006.1
Enantioselective syntheses of indolizidines (−)-219F and (−)-221I have been achieved and the relative stereochemistries of natural 219F and 221I were determined by the present synthesis. A levorotatory indolizidine, corresponding to one proposed structure for 193E, was also synthesized, but was found to differ from 193E. It seems likely that natural 193E is the 8-epimer of the synthesized indolizidine