... mixture was separated by preparative TIC (CHCla-MeOH = 20:1) and their structures were confirmed on the basis of the chemical shift of the H—3eq atom of 12aa-d and 1235.“ in the 'H—NHR spectrum: the H—3eq chemical shift of a ... 7. C. Shimizu, K. Achiwa, T. Hiyazawa, S ...