Asymmetric synthesis of 3,5-disubstituted indolizidines by intermolecular addition of an allylsilane on an N-acyliminium ion
摘要:
A diastereoselective synthesis of 3,5-disubstituted indolizidines based on an intermolecular addition of an allylsilane on an acyliminium ion derived from (S)-pyroglutamic acid is described. The synthetic potential of this methodology is demonstrated by the enantioselective synthesis of (-)-indolizidine 195B, (-)-indolizidine 223AB, (+)-monomorine and (-)-3-butyl-5-propyl indolizidine. (c) 2006 Elsevier Ltd. All rights reserved.
Synthesis of indolizidines (−)-195B, (−)-223AB and (−)-239AB: (2S,5R)-1-[(benzyloxy)carbonyl]-2-methoxycarbonyl-5-(4-pentenyl)pyrrolidine as a versatile chiral building block
indolizidines, (−)-195B, (−)-223AB and (−)-239AB are described. The employed strategy is based on the utilization of the common enantiopure trans 2,5-disubstitutedpyrrolidine 3, which is assembled by addition of pent-4-enylcopper to N-acyl iminium ion derived from (S)-proline.
An enantioselective access to (−)-indolizidine alkaloids167B, 209D, 239AB, 195B and (−)-monomorine from a new chiral synthon is described. The use of (S)-3-(Cbz-amino)-4-(tert-butyldimethylsilyloxy)butanal, obtained from l-aspartic acid, has provided efficient access of the indolizidine frame work through a Horner–Wadsworth–Emmons reaction and reductive cyclization as the key steps.
A General Approach to 3-<i>n</i>-Butyl-5-alkylindolizidines: Total Synthesis of (−)-Indolizidine 195B
作者:Steven R. Angle、Musong Kim
DOI:10.1021/jo7015423
日期:2007.11.1
Indolizidine type alkaloids have been attractive synthetic targets due to their biological activity. The total synthesis of (−)-indolizidine 195B via a general route, which could potentially be used to prepare other indolizidine alkaloids such as (−)-gephyrotoxin223AB and (−)-myrmicarin 237A, is described.
Total Synthesis of (+-)-Monomorine I and (+-)-Indolizidine 195B by an Aza-[2,3]-Wittig Rearrangement of a Vinylaziridine.
作者:Peter Somfai、Tomas Jarevång、Ulf M. Lindström、Anette Svensson、M. Hanfland、E. Dooryhee
DOI:10.3891/acta.chem.scand.51-1024
日期:——
A novel synthesis of (+/-)-monomorine I (1) and (+/-)-indolizidine 195B (2) is described in which the key step is the highly efficient aza-[2,3]-Wittigrearrangement of vinylaziridine 12 into tetrahydropyridine 13. Functional group manipulation then gave ketone 16 which could be converted into the target alkaloids by reductive amination (1:2 1.5:1).