Synthesis of (−)-(<i>R</i>)-Pyrrolam A and Studies on Its Stability: A Caveat on Computational Methods
作者:Rhett T. Watson、Vinayak K. Gore、Kishan R. Chandupatla、R. Karl Dieter、James P. Snyder
DOI:10.1021/jo049460r
日期:2004.9.1
The asymmetric synthesis of (−)-(R)-pyrrolam A was achieved in three operations from N-Boc pyrrolidine via an α-(N-carbamoyl)alkylcuprate vinylation reaction followed by N-Boc deprotection and cyclization. One-pot deprotection−cyclization procedures led to mixtures of pyrrolam A and its double bond isomers. These isomerization events could be circumvented by use of a two-step procedure. To guide aspects
Firstsynthesis of pyrrolam A (1), a pyrrolizidine alkaloid from Streptomyces olivaceus, was accomplished. The SmI2-mediated intramolecular coupling reaction between a bromoalkyl and ynamide group gave solely a cyclized product, which was converted to pyrrolam A (1) efficiently.
Asymmetric synthesis of (−)-(R)-pyrrolam A starting from (S)-malic acid
作者:Pei Qiang Huang、Quan Feng Chen、Chang Lin Chen、Hong Kui Zhang
DOI:10.1016/s0957-4166(99)00395-x
日期:1999.9
An asymmetricsynthesis of natural (−)-pyrrolam A starting from natural (S)-malic acid is described. The stereogenic center was established via a highly trans-diastereoselective reductive alkylation procedure. A tandem base-induced intramolecular amide N-substitution and tosic acid elimination led to the target molecule.
Short Syntheses of (-)-<b>(</b>
<b><i>R</i></b>
<b>)</b>-Pyrrolam A and (1<b><i>S</i></b>)-1-Hydroxyindolizidin-3-one
作者:Rainer Schobert、André Wicklein
DOI:10.1055/s-2007-966035
日期:——
(-)-( R)-Pyrrolam A was prepared in five steps, 95% ee and 25% yield, from ( R)-benzyl prolinate. Closure of the pyrrolidine ring was effected by a domino addition-Wittig alkenation reaction with ylide Ph 3 PCCO, immobilized on a polystyrene resin. An indolizidinone was obtained likewise from ( R)-benzyl pipecolate. The reduction of 1-ketopyrrolizidinones and 1-ketoindolizidinones is described.
(-)-(R)-Pyrrolam A 由 (R)-脯氨酸苄酯分五步制备,95% ee 和 25% 产率。吡咯烷环的闭合通过与叶立德 Ph 3 PCCO 的多米诺加成-维蒂希烯化反应实现,固定在聚苯乙烯树脂上。同样由(R)-苄基哌可酸得到吲哚齐酮。描述了 1-ketopyrrolizidinones 和 1-ketoindolizidinones 的还原。
An efficient route to the pyrrolizidine ring system via an N-acyl anion cyclisation process
作者:Anthony Murray、George R. Proctor、P.John Murray
DOI:10.1016/0040-4020(96)00049-x
日期:1996.3
An enantioselective route to the pyrrolizidineringsystem has been developed which uses an N-acyl anion cyclisation reaction as the key step. This methodology has provided the natural pyrrolizidines (−)-(1R, 8S)-1-hydroxy-pyrrolizidine 7, (−)-pyrrolizidin-1-ene-3-one 9 and (±)-trachelanthamidine 14. Extension of the process to an N-propionyl substrate provides ready access to a series of 2-methyl