COMPARISON OF CRYSTAL AND SOLUTION STRUCTURES AND H-1 AND C-13 CHEMICAL-SHIFTS FOR GRANDIFLORENIC ACID, KAURENOIC ACID, AND MONOGINOIC ACID

The crystal structure of monoginoic acid, 3, is determined acid compar ed with previously reported structures of kauradienoic acid, 1, acid k aurenoic acid, 2. H-1 and C-13 chemical shifts are assigned for all th ree diterpenes and solution and crystal structure conformations are co nfirmed 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.