Bridged thiazolium salts as models for thiamin: NMR, crystallographic and molecular mechanics studies

Abstract

NMR data for the bridged thiazolium salts 1b and c and thiazole-2(3H)-thiones 2b and c are described which allow their conformations in solution to be deduced. These are in full agreement with the X-ray crystal structures for 2b and c. The structures and conformations of the two atropisomers of the substituted thiazole-2(3H)-thiones 6 and 7 have also been deduced. Molecular mechanics calculations agree with the deduced conformations and have been used to predict the strain involved in the bridged thiazolium salts and the degree to which this strain is relieved in some of their reactions.