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| 1.
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Fujii, Tozo ; Ohba, Masashi
概要:
8-Hydroxyprotoemetine [(-)-2f], an aldehyde of biogenetic interest, has been synthesized for the first time from the tri
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cyclic ester (-)-5 through the intermediate (-)-6. Wolff-Kishner reduction of (-)-2f produced the 2-ethyl congener (-)-2g. As a result of these syntheses, the circular dichroism (CD) spectra of (-)-2f・HClO_4 and (-)-2g in 0.1 N aqueous HCl and in EtOH, together with those of the Alangium alkaloids ankorine (2d) and alancine (2e), are now availale.
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| 2.
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Fujii, Tozo ; Yoshifuji, Shigeyuki ; Ohba, Masashi
概要:
A highly stereoselective, efficient synthetic route to ethyl trans-5-ethyl-2-oxo-4-piperidineacetate (11a) from 1-benzyl-2,4-dioxo-5-ethylpiperidine (2) is described. The steps involved are
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conversion of 2 into 1-benzyl-5-ethyl-2-oxo-1,2,5,6-tetrahydropyridine (6) through the lactam alcohol (5), the Michael condensation of 6 with diethyl malonate followed by alkaline hydrolysis, decarboxylation of the resulting trans-lactam dicarboxylic acid (8a) to the trans-lactam acid (9a), and debenzylation of 9a followed by esterification.
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| 3.
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Fujii, Tozo ; Ohba, Masashi ; Yoshifuji, Shigeyuki ; Akiyama, Shigeaki
概要:
In order to investigate the effect of an N-substituent on thermal cis-trans isomerization of the 5-ethyl-2-oxo-4-piperid
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ineacetic acid system, the N-alkyl analogs (±)-1b, c and (±)-2b, c and the N-(2-arylethyl) analogs (-)-1f, g, i and (+)-2f, g, i were separately heated neat at 180℃, and the propress of their cis-trans isomerization reactions was followed by determining the isomer ratios in the reaction mixtures according to the previously reported C-13 nuclear magnetic resonance spectroscopic method. It has been found that in all cases the reaction comes to equilibrium within 28-130 min, when the cis and trans isomers exist in a ration of 1 : 2. These results together with those obtained previously with the analogs (±)-1a, d, e, (-)-1h, (±)-2a, d, e, and (+)-2h indicate that a higher and/or bulkier N-substituent tends to decrease the rate of cis-trans isomerization of the 5-ethyl-2-oxo-4-piperidineacetic acid system, which is a useful synthon for the synthesis of benzo-[a] quinolizidine-type Alangium alkaloids. Among the substrates used in the present equilibration study, (±)-1b, c and (±)-2b, c were prepared from the corresponding N-unsubstituted lactam esters (±)-3 and (±)-7 by the"lactim ether method."
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| 4.
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Fujii, Tozo ; Ohba, Masashi
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| 5.
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Fujii, Tozo ; Ohba, Masashi ; Akiyama, Shigeaki
概要:
In boiling 2.5 N solution of KOH in 40% (w/w) aqueous EtOH, the lactams (±)-5a, b, d were hydrolyzed to an extent of 75-
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98% within 8-20 h, attaining equilibrium with the corresponding ω-amino acid derivatives (±)-6a, b, d. The potassium salt (±)-8,generated in situ from the translactam acid (±)-7,was equilibrated with the ring-opened product (±)-6f and the recyclized cis isomer (±)-5f in a ratio of 57 : 15 : 28 within ca. 45 h under similar reaction conditions. The cis-N-(2-arylethyl) analog (-)-9 was converted into the trans-lactam acid (+)-13,a key synthetic precursor for the 8-hydroxy-9,10-dimethoxybenzo [a] quinolizidine-type Alangium alkaloids, through application of such alkaline hydrolytic cis-trans equilibration followed by debenzylation.
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| 6.
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Fujii, Tozo ; Ohba, Masashi ; Kawamura, Hitoshi ; Nakashio, Yoshiyuki ; Honda, Kei ; Matsubara, Satoshi
概要:
Both enantiomers [(1'R)-6 and (1'S)-6] of N6-(1,3-dimethyl-2- butenyl)adenine and their 9-β-D-ribofuranosides [(1''R)-16
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and (1''S)-16] have been synthesized for the first time from both enantiomers of alanine (15) in nine steps. These aglycones and nucleosides, together with N6-(3- methyl-2-butenyl)adenine (5) and its 9-β-D-ribofuranoside (18) as well as 9- β-D-ribofuranosyl-cis-zeatin (20) and 9-(2-deoxy-β-D-ribofuranosyl)-cis- zeatin (19), were tested for cytokinin activity in the tobacco callus bioassay. The order of their activity was 5> (1'R)-6 > (1''R)-16≃18>(1'S)- 6>(1''S)-16>20>19. The bioassay results are compared with those obtained previously for the derivatives modified analogously in the N6-substituent in the cis- and trans-zeatin series.
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| 7.
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Fujii, Tozo ; Ohba, Masashi ; Kawamura, Hitoshi ; Haneishi, Tsuyoshi ; Matsubara, Satoshi
概要:
(1'S)-1'-Methyl-cis-zeatin [(1'S)-2] and its 9-β-D-ribofuranoside [(1'S)- 4] were synthesized from L-alanine through [S-
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(Z)]-4-amino-2-methyl-2- penten-1-ol ethanedioate [(S)-3]. Condensations of 2-hydroxy-6- methylthiopurine (16) with the trans-isomeric amine salt [(S)-15], its enantiomer [(R)-15], and the racemic modification [(±)-15] furnished (1'S)- , (1'R)-, and (±)-2-hydroxyl-1'-methyl-trans-zeatins (6), respectively. A similar condensation of 16 with methylamine yielded 2-hydroxy-N6- methyladenine (7). These adenine derivatives were tested for cytokinin activity in the tobacco callus bioassay, and the order of their activity was (1'R)-6>(±)-6>(1'S)-2>7; on the other hand, (1''S)-4 and (1'S)-6 were completely inactive at 0.1-100 μM and 0.01-10 μM concentrations, respectively. As a result of the above syntheses of (1'R)-6, (1'S)-6, (±)- 6, and 7, the gross structures of a marine green alga cytokinin and of a blue coral cytokinin were established to be 6 and 7, respectively.
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| 8.
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Evidente, Antonio ; Piccialli, Gennaro ; Sisto, Angelo ; Ohba, Masashi ; Honda, Kei ; Fujii, Tozo
概要:
cis-Zeatin (3a) and its 9-(2-deoxy-β-D-ribofuranosyl) derivative (3c) have been synthesized from N-[(1,1-dimethylethoxy)
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carbonyl]glycine methyl ester (5) in 5 steps by adopting the "α-amino aldehyde/olefination" technology. The new cis-zeatin derivative (3c), its trans isomer (1c), and known trans-zeatin 9-β-D-riboside (1b) were tested for cytokinin activity in the stimulation of chlorophyll biosynthesis in etiolated cucumber cotyledons. The riboside 1b turned out to be the most active cytokinin among them, while the deoxyribosides 1c and 3c showed a marked decrease and a total loss, respectively, of cytokinin activity.
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| 9.
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Fujii, Tozo ; Saito, Toru ; Chikazawa, Jun ; Nakamura, Yuko ; Ohba, Masashi
概要:
Four-step synthetic routes from 3-methyladenine (10) to 7-benzyl-N6,3-dimethyladenine (1b) and 7-benzyl-1,2-dihydro-1,3-dimethyladenine (2b), selected as models for the marine sponge alkaloids agelasimine-A (1a) and
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agelasimine-B (2a), respectively, have been established. The key steps involved are regioselective methylations of 7-benzyl-3-methyladenine (8) and 7-benzyl-1,2-dihydro-3-methyladenine (11). The reaction of 1b with acetic anhydride in pyridine was found to give the monocyclic imidazole derivative 29b. A similar acetylation of 2b yielded the N6-acetyl derivative 20b. When treated with boiling H2O, 20b afforded 7-benzyl-2,3-dimethylhypoxanthine (21b) and a compound inferred to be the dihydrohypoxanthine derivative 30. Probable pathways to 29b from 1b and to 21b and 30 from 20b are proposed.
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| 10.
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Fujii, Tozo ; Ohba, Masashi ; Tsuchida, Michiko ; Saito, Kiyoe ; Hirano, Yuko ; Sakaguchi, Jun
概要:
A quantitative analytical study to determine the isomer ratios of the 6-piperidones (type 7) and 2-piperidones (type 5)
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produced by the mercuric acetate-edetic acid (EDTA) oxidation of 1-(2-aryl-2-hydroxyethyl)-3-alkylpiperidines (±)-4c, d, f, h, 4e, g, i, j, and (±)-38 was carried out. It has been found that all the substrates with a benzyloxy group in the aryl moiety, regardless of its location, undergo oxidation at the 6-position preferentially as compared with the debenzyloxy derivatives such as (±)-4a, b. Comparison of the quantitative data from 4e and (±)-4f with those from (±)-4b indicated that the cis acetate chain at the 4-position increases the extent of the 6-oxidation, whereas a trans acetate chain at the same position has little effect. These two factors enhance the practical value of the "cincholoipon-incorporating method" for chiral syntheses of the 1-type Alangium alkaloids, in which the mercuric acetate-EDTA oxidation of 4e, g, i, j to the 6-piperidones (type 3)is one of the key synthetic operations.
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