Studies in sigmatropic rearrangements of N-prenylindole derivatives – a formal enantiomerically pure synthesis of tryprostatin B

A. Sofia P. Cardoso; M. Manuel B. Marques; Natarajan Srinivasan; Sundaresan Prabhakar; Ana M. Lobo; Henry S. Rzepa

doi:10.1039/B606457D

Studies in sigmatropic rearrangements of N-prenylindole derivatives – a formal enantiomerically pure synthesis of tryprostatin B

A. Sofia P. Cardoso,^a^b M. Manuel B. Marques,^a^b Natarajan Srinivasan,^a^b Sundaresan Prabhakar,*^a^b Ana M. Lobo*^a^b and Henry S. Rzepa*^c

Author affiliations

* Corresponding authors

^a Chemistry Department, REQUIMTE/CQFB, Faculty of Sciences and Technology, New University of Lisbon, Monte de Caparica, Portugal
E-mail: sprabhakar@fct.unl.pt, aml@fct.unl.pt
Fax: +351 212948550

^b SINTOR-UNINOVA, Monte de Caparica, Portugal

^c Chemistry Department, Imperial College London, South Kensington Campus, London, UK
E-mail: h.rzepa@ic.ac.uk

Abstract

Rearrangement of N^a-prenyl-N^b-acetyltryptamine, induced by BF₃·Et₂O at low temperature, leads to a 2-prenyl derivative, and thence to the tricyclic tryptamine 7 and the indoline 8. Similarly, N^a-prenyl-N^b-phthaloyl-L-tryptophan methyl ester furnished the corresponding 2-prenyl derivative 16, a known advanced precursor of tryprostatin B. Density functional (B3LYP) calculations for the putative rearrangement transition state for N-prenylskatole show that prior coordination of BF₃ to the indolic nitrogen changes the character of the subsequent sigmatropic pericyclic shifts from being entirely covalent to acquiring a significant degree of ionic character. The shifting prenyl group favours the endo over the exo mode of the transition state by 4.1 kcal mol⁻¹.

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Publication details

The article was received on 22 May 2006, accepted on 12 Sep 2006 and first published on 28 Sep 2006

Article type: Paper

DOI: 10.1039/B606457D

Citation: Org. Biomol. Chem., 2006,4, 3966-3972

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Studies in sigmatropic rearrangements of N-prenylindole derivatives – a formal enantiomerically pure synthesis of tryprostatin B

A. S. P. Cardoso, M. M. B. Marques, N. Srinivasan, S. Prabhakar, A. M. Lobo and H. S. Rzepa, Org. Biomol. Chem., 2006, 4, 3966
DOI: 10.1039/B606457D
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Organic & Biomolecular Chemistry

Studies in sigmatropic rearrangements of N-prenylindole derivatives – a formal enantiomerically pure synthesis of tryprostatin B

Abstract

Supplementary files

Publication details

Studies in sigmatropic rearrangements of N-prenylindole derivatives – a formal enantiomerically pure synthesis of tryprostatin B

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