Comparison of crystal and solution structures and H-1 and C-13 chemical shifts for grandiflorenic acid, kaurenoic acid, and monoginoic acid

Abstract

The crystal structure of monoginoic acid, 3, is determined acid compared with previously reported structures of kauradienoic acid, 1, acid kaurenoic acid, 2. H-1 and C-13 chemical shifts are assigned for all three diterpenes and solution and crystal structure conformations are confirmed with the aid of solution NOE measurements. The overall shapes of 2 and 3 are very similar while 1 is significantly dissimilar. These differences may be partially responsible for the reported greater in vitro uterotropic activity of 1, relative to 2 and 3.