ONE-POT DIASTEREOSELECTIVE SYNTHESIS OF CHIRAL TRICYCLIC l-CYSTEINE AND d-PENICILLAMINE DERIVATIVES: A LABORATORY EXPERIMENT

Abstract

Recebido em 10/07/2019; aceito em 22/08/2019; publicado na web em 21/11/2019 A one-pot diastereoselective synthesis of thiazolidine-ring fused systems derived from enantiomerically pure amino acids, l-cysteine or d-penicillamine, and achiral succindialdehyde is described as an experiment to be carried out by upper-division undergraduate students in a laboratory classroom. Reactions were performed under mild conditions, the products were isolated through simple experimental procedures and fully characterized. This study combines organic synthesis, determination of the purity of compounds (TLC analysis and melting point measurements), optical activity measurements as well as structural analysis (interpretation of 1D NMR and 2D NMR spectra). It offers a platform for the discussion of important organic chemistry concepts such as diastereoselectivity, kinetic control vs thermodynamic control and cyclization reactions via nucleophilic addition to imines/ iminium cations.

Adaptation of Chiral GC into existing undergraduate labs to improve student appreciation of stereochemistry

“…Methods for determining the absolute configuration of chiral molecules that have either been reported or are in use in most undergraduate curricula rely either on acid-base extraction followed by NMR or polarimetry 2,18,19 or on the determination of diastereomeric ratios of chiral derivatives using NMR, TLC, GC or HPLC analysis. [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] Herein described is how the addition and utility of gas chromatography (GC) data to two undergraduate organic chemistry experiments enables a better student experience of (1) the fact that the two sources of carvone lead to different isomers and (2) how the asymmetric reduction of acetophenone with a CBS catalyst produces an excess of one enantiomer compared to the non-catalyzed reaction which produces a racemic mixture of alcohol. The carvone experiment was completed in a single four-hour lab period, whereas the reduction experiment was conducted over two lab periods.…”