- Preparation of a tritiated ginkgolide
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A radiolabeled constituent of Ginkgo biloba, [3H]-ginkgolide B, was prepared in high specific radioactivity, providing a tool for studying neuromodulatory properties of ginkgolides. Ginkgolide B, a constituent of the tree Ginkgo biloba, was radiolabeled with the β-emitter tritium ([ 3H]) in two steps from ginkgolide C. First, a triflate precursor was prepared utilizing the selective reactivity of 7-OH in ginkgolide C; the triflate was then reduced with sodium borotritide to yield tritiated ginkgolide B ([3H]GB) in good yield and high specific activity. The tritiated ginkgolide will be an important tool for studying neuromodulatory properties of ginkgolides.
- Str?mgaard, Kristian,Suehiro, Makiko,Nakanishi, Koji
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- Isolation of ginkgolides A, B, C, J and bilobalide from G. biloba extracts
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Ginkgolides A, B, C and J, together with bilobalide, are unique terpenoid components of the Ginkgo biloba tree. Due to similar chemical properties, their separation is quite tedious. We have developed an efficient and rapid protocol for separation of individual ginkgolides and bilobalide from G. biloba extracts. The procedure takes advantage of enhanced susceptibility of ginkgolides B and C to benzylation and the ease of separation of these products from ginkgolides A and J which do not react. The protocol is applicable to the previously reported enriched extracts prepared from G. biloba leaves. A single chromatographic step prior to benzylation provides bilobalide and mixture of ginkgolides A, B, C, and J. After benzylation, the individual ginkgolides are separated by chromatography.
- Jaracz, Stanislav,Malik, Shahid,Nakanishi, Koji
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p. 2897 - 2902
(2007/10/03)
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- INTRAMOLECULAR AND INTERMOLECULAR HYDROXYL REACTIVITY DIFFERENCES IN GINKGOLIDES A, B AND C AND THEIR CHEMICAL APPLICATIONS
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An investigation of the chemistry of ginkgolides A, B and C (1) has revealed an unusual interaction between the hydroxyl groups at C(1) and C(10) which activates their deprotonation to give 2 and provides a method for the interconversion of 1C and 1B.The ginkgolide 7-enol system 7 is more stable than the corresponding 7-keto form 6, which is easily made by selective Jones oxydation of ginkgolide C.
- Corey, E. J.,Rao, K. Srinivas,Ghosh, Arun K.
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p. 6955 - 6958
(2007/10/02)
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- Chemistry of Ginkgolides, IV. Synthesis of Ginkgolide B from Ginkgolide C
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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.
- Weinges, Klaus,Schick, Hartmut
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