Cis-diastereoselectivity in pictet-spengler reactions of L-tryptophan and electronic circular dichroism studies.

Abstract

The diastereoselective synthesis of optically active 1,3-disubstituted tetrahydro-β-carbolines using polar protic Pictet-Spengler cyclization of (S)-tryptophan methyl ester with five aldehydes RCHO (R═CH(3), C(2)H(5), C(3)H(7), C(4)H(9), and C(6)H(5)) was studied. As an alternate route, the cyclization of (S)-tryptophan with the same aldehydes and subsequent methylation of the resulting tetrahydro-β-carboline carboxylic acids were also performed for comparison. (13)C NMR and electronic circular dichroism (ECD) studies and time-dependent density functional theory ECD calculations data established the relative 1,3 cis/trans and the absolute configuration (1S,3S/ 1R,3S) of the synthesized compounds. The solid-state and solution ECD study of the prepared compounds, supported by ECD calculation and X-ray data, afforded a reliable ECD method for the configurational assignment of 1,3-disubstituted tetrahydro-β-carbolines and revealed the stereochemical factors that determine the characteristic ECD data.

DOI: 10.1002/chir.22070

Cite this paper

@article{Rashid2012CisdiastereoselectivityIP, title={Cis-diastereoselectivity in pictet-spengler reactions of L-tryptophan and electronic circular dichroism studies.}, author={Naghmana Rashid and S . Munir Alam and M. Masood ul Hasan and Naeema Khan and Khalid M. Khan and Helmut Duddeck and Gennaro Pescitelli and Agnes Ken{\'e}z and S{\'a}ndor Antus and Tibor Kurt{\'a}n}, journal={Chirality}, year={2012}, volume={24 10}, pages={789-95} }