Stereoselective synthesis of swainsonines from pyridines
作者:Gerres Heimgärtner、Dirk Raatz、Oliver Reiser
DOI:10.1016/j.tet.2004.10.086
日期:2005.1
efficient synthesis of (−)-swainsonine and (−)-2,8a-di-epi-swainsonine was developed starting from readily available 2-pyridinecarbaldehyde and 3-hydroxypyridine. In particular, it was demonstrated that the mixture of simple indolizidines, i.e. lentiginosine and epi-lentiginosine, being readily available by a number of different synthetic routes, can be directly converted to swainsonine.
Enantiocontrolled Preparation of Indolizidines: Synthesis of (−)-2-Epilentiginosine and (+)-Lentiginosine
作者:Martin O. Rasmussen、Philippe Delair、Andrew E. Greene
DOI:10.1021/jo010298r
日期:2001.8.1
A highly stereoselective approach to (-)-2-epilentiginosine and (+)-lentiginosine has been developed based on a diastereofacially selective cycloaddition of dichloroketene with a chiral dienol ether. The two naturally occurring indolizidines are each obtained enantioselectively (> or = 99:1) in ca. 8.5% overall yield.
lactam as a new chiral building block for alkaloid synthesis. Lipase-catalyzed kinetic resolution of hydroxylactam 8, followed by isolation–racemization of the chiral acetoxylactam 9 provided the opticallypure hydroxylactam 8 in 96.0% yield with >99% ee after five cycles of kinetic resolution–racemization process. Chemical transformation of (S)-hydroxylactam 8 furnished chiral (−)-2-epi-lentiginosine