Room-temperature (H-1, C-13) variable-temperature (H-1) NMR studies on spinosin

Spinosin, a C-glycoside flavonoid, was isolated from the plant Desmodium to rtuosum (Sw.) DC. The H-1 and C-13 NMR data acquired at room temperature ex hibited doubling of signals, suggesting the presence of two rotamers in sol ution. Variable-temperature H-1 NMR experiments confirmed this hypothesis. T-ROESY experiments in conjunction with theoretical (MM2) calculations supp orted the proposal that the two rotamers interchange via rotation about the C-6-C-1 " bond. The spectral data were completely assigned using H-1-.H-1 COSY, HMQC, HSQC and HMBC experiments. Copyright (C) 2000 John Wiley & Sons , Ltd.