Murrastifoline-F: First Total Synthesis, Atropo-Enantiomer Resolution, and Stereoanalysis of an Axially Chiral N,C-Coupled Biaryl Alkaloid

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• 作者：Gerhard Bringmann ; Stefan Tasler ; Heike Endress ; Jü ; rgen Kraus ; Kim Messer ; Michael Wohlfarth ; and Wolfram Lobin
• 刊名：Journal of the American Chemical Society
• 出版年：2001
• 出版时间：March 28, 2001
• 年：2001
• 卷：123
• 期：12
• 页码：2703 - 2711
• 全文大小：276K
• 年卷期：v.123,no.12(March 28, 2001)
• ISSN：1520-5126

文摘

The first total synthesis of the Murraya alkaloid murrastifoline-F (3), an unsymmetric, N,C-bondedheterobiarylic biscarbazole, is described. Starting from the likewise naturally occurring-but here syntheticallyprepared-"monomer" murrayafoline-A (6), lead tetraacetate-mediated oxidative non-phenolic biaryl couplinggives 3 as the main regioisomer. The existence of this natural product as a pair of stable atropo-enantiomerswas demonstrated analytically through LC-CD investigations. Preparatively, the racemate resolution succeededby O-demethylation, derivatization with Mosher's reagent, and chromatographic separation of the resultingdiastereomers. The absolute configurations of the atropisomers were assigned by CD spectroscopy in combinationwith quantum chemical CD calculations at the stage of the alkaloid 3 and by ROESY experiments of thediastereomeric Mosher derivatives. In the root extract of the curry leaf plant Murraya koenigii (Rutaceae),murrastifoline-F (3) was found to exist as a 56:44 mixture in favor of the M-enantiomer, by LC-CD coupling.