PURPOSE: To convert ginkgolide B into ginkgolide C which is a potent inhibitor of a PAF-acether in two steps by reacting ginkgolide C with a sulfonic acid anhydride, then with a boron hydride in a nonprotic solvent.
CONSTITUTION: This ginkgolide B of formula II is obtained by first reacting ginkgolide C of formula I with a sulfonic acid anhydride (suitably trifluoromethane sulfonic acid anhydride) preferably in pyridine to obtain C-7 sulfonate of the ginkgolide C, and then reacting the obtained compound with a boron hydride (suitably, sodium borohydride or tetrabutylammonium borohydride) in a nonprotic solvent (suitably in THF) at preferably a temp. of 10-30°C for 15 min-3 hr for eliminating the C-7 group of the C-7 sulfonate of the gingkolide C. Further, the reaction of the gingkolide C with the sulfonic acid anhydride is preferably carried out at a temp. of (-)20-35°C for 15 min-3 hr.
DAFUNIE MISHIERU
REBORO JIYATSUKU
TAN BANNPOON
