Antisweet Natural Products. IX. Structures of Gymnemic Acids XV-XVIII from Gymnema sylvestre R. BR. V

抄録

Systematic separation of the saponin fraction of the leaves of Gymnema sylvestre has led to the isolation of four new saponins, gymnemic acids XV-XVIII, as antisweet substances. The structures were elucidated by spectral and chemical studies. Gymnemic acids XV-XVIII, are 21-O-2-methylbutyryl-22-O-2-methylcrotonoyl, 16, 22-O-bis-2-methylcrotonoyl, 21-O-benzoyl, and 28-O-benzoyl gymnemagenin 3-O-gluculonides, respectively. Gymnemic acids VIII and IX that we had named in the previous paper were renamed gymnemic acids XV and XVI, respectively.