Chemie der Ginkgolide, IV. Herstellung von Ginkgolid B aus Ginkgolid C

Abstract

Chemistry of Ginkgolides, IV1). – Synthesis of Ginkgolide B from Ginkgolide C The reaction of ginkgolide C (3) with tert‐butylchlorodiphenylsilane results exclusively in the formation of the 1‐O‐tert‐butyldiphenylsilyl ether 5, which when treated with O‐phenylchlorothioformate leads to the 7‐phenyloxythiocarbonyl derivative 6. The reduction of 6 with tributyltin hydride/AIBN yields the 1‐O‐tert‐butyldiphenylsilyl ether 7 of ginkgolide B (2). Removal of the silyl protective group with tetrabutylammonium fluoride gives pure ginkgolide B (2). The structures of the reaction products were confirmed by analytical and spectroscopic methods.

Ginkgolides and Glycine Receptors: A Structure–Activity Relationship Study

“…Although a selective silylation of 1-OH has been carried out by Weinges [40] the mechanism and scope of this reaction are not clear. We found that selective derivatization of 1-OH can be achieved by acyl migration from 6-O (iso-GC derivatives) via a six-membered cycle intermediate (Scheme 3).…”

“…[35] However, acid-catalyzed esterification, [36] reaction of GC (3) with alkyl and aryl sulfonyl halides in the presence of pyridine [37,38] as well as silylation [39] takes place at 7-OH; a selective silylation at 1-OH in the presence of imidazole has also been described. [40] The use of solid-phase synthesis (SPS) for the preparation of ginkgolide derivatives appeared to be particularly attractive, as the presence of multiple hydroxyl groups provides several options for connecting points. Hence various strategies were investigated, including silicon, [41,42] sulfonyl, [43] Wang, [44,45] and Rink amide [46] linkers.…”

Synthesis and biological studies of a new ginkgolide C derivative: Evidence that the cardioprotective effect of ginkgolides is unrelated to PAF inhibition

“…The four hydroxyl groups of ginkgolide C show highly different reactivities [Corey et al, 1992;Weinges and Schick, 1991;Weinges et al, 1993]. Apart from the tertiary hydroxyl group on C 3 , the 7-hydroxyl function is generally the least reactive of the three other groups.…”

Influence of lipophilicity and stereochemistry at the C7 position on the cardioprotective and antioxidant effect of ginkgolides during rat heart ischemia and reperfusion

“…As a consequence of increased steric hindrance in its environment, the C 7 -hydroxyl group is the least reactive of the secondary hydroxyl groups of 1 [Corey et al, 1992;Weinges and Schick, 1991;Weinges et al, 1993]. However, selective oxidation or acetylation of the C 7 -hydroxyl group of 1 without protection of the other secondary hydroxyl groups have been reported [Corey et al, 1992;Jaracz et al, 2002].…”