1H and 13C NMR study of tetrahydro-1,4-benzothiazepine conformationsElectronic supplementary information (ESI) available: crystal data, structure refinement and a perspective view of the X-ray crystal structure of 1. See http://www.rsc.org/suppdata/p2/b2/b205768a/

Abstract

The variable temperature (298–178 K) 1H NMR spectra of tetrahydro-1,4-benzothiazepines 1–10 are described and discussed. Compounds 2–10 exist as two puckered mirror-image (enantiomorphic) conformers, with benzothiazepine ring chair-to-chair interconversion barriers of ca. 10 kcal mol−1 in CD2Cl2 solution. A similar interconversion was detected for compound 1, of lower symmetry. The ground state conformations of 1–10 were assigned on the basis of the magnitudes of 1H–1H vicinal coupling constants. The 1H and 13C NMR spectral assignments were determined by 1H–1H COSY, HETCOR, and NOESY experiments. The stereochemistry and conformation of compound 1 was further confirmed by a single crystal X-ray structure determination.