Studies in sigmatropic rearrangements of N-prenylindole derivatives--a formal enantiomerically pure synthesis of tryprostatin B |
| |
Authors: | Cardoso A Sofia P Marques M Manuel B Srinivasan Natarajan Prabhakar Sundaresan Lobo Ana M Rzepa Henry S |
| |
Institution: | Chemistry Department, REQUIMTE/CQFB, Faculty of Sciences and Technology, New University of Lisbon, 2829-516, Monte de Caparica, Portugal. |
| |
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). |
| |
Keywords: | |
本文献已被 PubMed 等数据库收录! |
|