| Budget Amount *help |
¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 1987: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 1986: ¥1,200,000 (Direct Cost: ¥1,200,000)
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| Research Abstract |
A series of congeners (I-IV) of the Alangium alkaloid ankorine (I), differing in oxidation state at the side chain, were synthesized through the "cincholoipon-incorporating route" as shown below.
1. The starting material selected for these syntheses was cincholoipon ethyl ester [(+)-V], and it was prepared from commercially available cinchonine in 50% overall yield according to the classical 7-step degradation procedure.
2. The ester (+)-V was then converted into the tricyclic amino ester (-)-VI, the key intermediate in the previous chiral synthesis of I, through the previously reported 10-step route.
3. The tricycle (-)-VI was converted into the target alancine (II) by alkaline hydrolysis and subsequent hydrogenolysis. Conversion of (-)-VI into 8-hydroxyprotoemetine (III), another target, was efeected by hydrogenolysis and subsequent i-Bu_2AlH reduction. Wolff-Kishner reduction of III gave the 3-ethyl congener IV, yet another target, in good yield.
4. An alternative synthetic route to I-IV was established by application of the "RuO_4 oxidation method".
5. To our surprise, the previously reported spectral data of "natural alancine" did not match those of the synthetic II,but matched those of its hydrochloride salt instead. It thus became evident that the physical, chemical, and spectral data reported by Schiff et al. for "natural alancine" were in reality those for II・HCl. With the completion of the above syntheses and characterization of II-IV, the search for these substances in the plant source may proceed.
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