A Quantitative Analysis of Proton Nuclear Magnetic Relaxation : Conformation Analysis of Substituted 5,1-Benzothiazocine and Its Homologue(Organic,Chemical)

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In addition to variable-temperature experiments and the analysis of vicinal coupling constants, a quantitative treatment of T_1 values and nuclear Overhauser effect (NOE) factors was applied to the conformation analysis of novel heterocycles, substituted 4,1-benzothiazepine (1) and 5,1-benzothiazocine (2). The most probable conformations of the seven- and eight-membered rings of 1 and 2, respectively, could be distinguished by comparing the observed T_1 values and NOE factors with those calculated for several possible conformers. By the quantitative analysis of T_1 values at -90.2℃ and at room temperature (24.5℃), 1 was found to be in an equilibrium state of rapid ring inversion between two chair forms in the ratio of 0.7:0.3 (at 24.5℃), and the major conformer was the chair form with 5-melhyl group equatorial. The X-ray analysis of 2 showed that the eight-membered ring adopted a boat-boat like conformation in the crystal. Although this conformation seemed to be consistent with most of the observed relaxation data obtained in solution, the significant shielding effect expected on H_<40>, was not observed. By a systematic search of the conformers, a boat-chair like conformer was found to satisfy all the observed relaxation and shielding data.
公益社団法人日本薬学会の論文
1987-03-25