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| 1.
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論文
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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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| 2.
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論文
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Fujii, Tozo ; Ohba, Masashi ; Akiyama, Shigeaki
概要:
New syntheses of the ipecac and Alangium alkaloids possessing the 9,10-dimethoxy- and 8-hydroxy-9,10-dimethoxybenzo [a]
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quinolizidine skeletons (types 1 and 2) have now become possible through generally applicable routes starting from 3-acetylpyridine (5). The routes involve the mercuric acetate-edetic acid oxidation of the 3-acetylpiperidine derivatives 9a, b or the alkaline ferricyanide oxidation of the quaternary salts (26a, b and 27a, b) of 3-acetylpyridine equivalents, Wolff-Kishner reduction of the acetyl group or reductive desulfurization of the thioketal group, sulfenylation-dehydrosulfenylation of the lactams 12a, b, Michael reaction of the α, β-unsaturated lactams 15a, b, and de-ethoxycarbonylation of the Michael adducts 16a, b as the main operations.
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| 3.
論文 |
論文
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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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