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| 1.
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論文
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Fujii, Tozo ; Ohba, Masashi ; Ali, Esahak ; Suzuki, Hitoshi ; Sakaguchi, Jun
概要:
The synthesis of (±)-9-demethylprotoemetinol [(±)-3d] was accomplished by LiAlH_4 reduction of the tricyclic ester (±)-5
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and subsequent debenzylation of the resulting tricyclic-alcohol (±)-10. Acetylation of (±)-3d with acetic anhydride and pyridine gave the diacetate (±)-11. The same sequence of reactions starting with (-)-5 afforded (-)-9-demethylprotoemetinol [(-)-3d] and the diacetate (-)-11 through (-)-10. Parallel synthetic routes starting with the isomeric tricyclic esters (±)-9 and (-)-9 produced (±)- and (-)-10-demethylprotoemetinols [(±)-4d and (-)-4d] and the corresponding diacetates [(±)-13 and (-)-13] through (±)-12 and (-)-12, respectively. The correctness of the structure and absolute stereochemistry of an Alangiutn alkaloid inferred to be 10-demethylprotoemetinol was confirmed by a direct comparison of its diacetate with synthetic (-)-13.
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| 2.
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Fujii, Tozo ; Ohba, Masashi ; Tachinami, Tsuyoshi ; Miyajima, Hisae
概要:
The first total synthesis of ochropposinine (1), a Neisosperma and Ochrosia alkaloid, has been accomplished in the form
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of a racemic modification by means of an initial coupling of the lactim ether (±)-3 with 5 and succeeding steps proceeding through the intermediates (±)-7,(±)-8,(±)-9,(±)-10,and (±)-11. A parallel synthetic route starting with (+)-3 produced the chiral target molecule (-)-1 via the intermediates (+)-7,(+)-8,(+)-9,10,and (-)-11. As a result, the absolute configuration of ochropposinine has been unequivocally established to be that represented by formula (-)-1.
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| 3.
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Fujii, Tozo ; Ohba, Masashi ; Tachinami, Takeshi ; Ohashi, Takako
概要:
A full account is given of the first racemic and chiral syntheses of 11-methoxydihydrocorynantheol [(-)-1], a candidate
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structure for the Neisosperma alkaloid ochromianine. Coupling of (±)-trans-6-ethoxy-3-ethyl-2,3,4,5-tetrahydro-4-pyridineacetic acid ethyl ester [(±)-6] with 2-chloro-1-(6-methoxy-1H-indol-3-yl)ethanone (4) in the presence of KBr produced the lactam ketone (±)-7,which was then converted into the lactam (±)-9 through the oxazolium salt (±)-8. Bischler-Napieralski cyclization of (±)-9 followed by catalytic hydrogenation gave the tetracyclic ester (±)-11. On reduction with LiAlH_4,(±)-11 yielded the racemic target (±)-1. A parallel synthetic route starting from (+)-6 and 4 afforded the chiral target (-)-1 via (+)-7,8,(+)-9,and (-)-11. Identity of synthetic (-)-1 with ochromianine unequivocally established the structure and absolute stereochemistry of this alkaloid.
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| 4.
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Fujii, Tozo ; Ohba, Masashi ; Sakari, Miwa ; Matsubara, Satoshi
概要:
(1'R)-1'-Methyl-cis-zeatin (2b) and its 9-β-D-ribofuranoside (4b) have been synthesized for the first time from D-alanin
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e (5) in 7 steps. The new cis-zeatin derivatives 2b and 4b, together with known cis-zeatin (2a), were tested for cytokinin activity in the tobacco callus and the lettuce seed germination bioassays. In both bioassays, the cytokinin activity was found to follow the order 2a>2b>4b, indicating that 2b and 4b were less active than the corresponding trans isomers 1b and 3b (natural cytokinins from Pseudomonas syringae pv savastanoi), respectively.
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| 5.
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Fujii, Tozo ; Ohba, Masashi ; Hatakeyama, Hiroshi
概要:
The chiral synthesis of (-)-9-demethyltubulosine [(-)-1] has been achieved for the first time via a "cincholoipon-incorporating route," which started from cincholoipon ethyl ester [(+)-7] and passed through the intermediates (-)-8,
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(-)-9, (+)-10, and (-t-)-11. As a result, the absolute configuration of the Alangium vitiense alkaloid 9-deniethyltubulosine has been unequivocally established to be that represented by formula (-)-1.
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