- Regioselective synthesis of nitrones by decarboxylative oxidation of N- alkyl-α-amino acids and application to the synthesis of 1-azabicyclic alkaloids
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Tungstate-catalyzed oxidation of N-alkyl-2a-amino acids with 30% H2O2 solution under phase-transfer conditions gives nitrones regioselectively in good yields: Using this method, stereodivergent synthesis of (R)- and (S)-4- (t-butyldimethylsilyloxy)-1-pyrroline N-oxides ((R)-17a and (S)-17a) was achieved. In addition, (R)- and (S)-3-(t-butyldimethylsilyloxy)-1-pyrroline N-oxides ((R)-45 and (S)-45) were prepared by catalytic oxidation of the corresponding chiral pyrrolidines in a regioselective manner. These chiral cyclic nitrones, 17 and 45 are versatile intermediates for the synthesis of optically active nitrogen heterocycles, since stereoselective additions of carbon nucleophiles to these chiral nitrones can be readily performed. Typically, ZnI2-mediated addition of ketene t-butyldimethylsilyi methyl acetal (29a): to (R)-17a gave the' cis-adduct, methyl (2R,4R)-[1,4-bis(t- butyldimethylsilyloxy)pyrrolidin-2-yl]acetate (cis-30). In contrast, the addition of lithium acetylides 34 to the nitrone (R)-17a gave the trans- adducts, (2S,4R)-2-(1-alkynyl)-4-(t-butyldimethylsilyloxy)-1- hydroxypyrrolidines trans-35. These adducts are useful intermediates for syntheses of the nitrogen heterocycles (3R,5R)-1-aza-3- hydroxybicyclo[3.3.0]octane (37) and (6R,8R)-1-aza-8- hydroxybicyclo[4.30]nonane (38), respectively. The ZnI2-mediated addition of ketene silyl acetal 29a to the nitrone (R)-45 gave methyl (2S, 3R)-[1,3- bis(t-butyldimethylsilyloxy)pyrrolidin-2-yl]acetate (trans-50a), which was used for asymmetric synthesis of the Geissman-Waiss lactone ((-)-49).
- Ohtake, Hiroaki,Imada, Yasushi,Murahashi, Shun-Ichi
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p. 2737 - 2754
(2007/10/03)
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- Synthesis of (R)- and (S)-3-(tert-butyldimethylsilyloxy)-1-pyrroline N- oxides - Chiral nitrones for synthesis of biologically active pyrrolidine derivative, Geissman-Waiss lactone
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Tungstate-catalyzed oxidation of O-tert-butyldimethylsilyl (O-TBDMS) protected (R)-3-hydroxypyrrolidine ((R)2), derived from trans-4-hydroxy-L- proline, gave O-TBDMS protected (R)-3-hydroxy-1-pyrroline N-oxide ((R)1), which is a new chiral precursor for the synthesis of Geissman-Waiss lactone. The enantiomeric nitrone (S)-1 was also prepared by the oxidation of (S)-2 derived from L-malic acid.
- Murahashi, Shun-Ichi,Ohtake, Hiroaki,Imada, Yasushi
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p. 2765 - 2766
(2007/10/03)
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- Facile synthesis of (+)- and (-)-Geissman-Waiss lactones
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(+)- and (-)- Geissman-Waiss lactones (1), were prepared from the readily accessible (4R, 5R)- and (4S, 5S)-5-allyl-4-methoxy-2-oxazolidinones [(+)- and (-)-7], respectively, in a highly stereocontrolled manner from the previously reported building block, 3-[(1S)-2-exo-alkoxy-1-apocamphanecarbonyl]-2-oxazolones (4).
- Kouyama, Takafumi,Matsunaga, Hirofumi,Ishizuka, Tadao,Kunieda, Takehisa
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p. 479 - 486
(2007/10/03)
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- Cycloaddition Reaction of Cyclic Enecarbamates and Enamides With Ketenes. A Short and Efficient Synthesis of the Geissman-Waiss Lactone.
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The synthesis of several 2-aza-bicycloheptan-6-ones has been achieved in a regiospecific manner through a cycloaddition reaction between five-membered cyclic enecarbamates and enamides and free ketenes.The synthetic potential of this new meth
- Faria, Antonio R. de,Matos, Carlos Roberto R.,Correia, Carlos Roque D.
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- SYNTHESIS OF N-ETHOXYCARBONYLMETHYL GEISSMAN-WAISS LACTONE: UNUSUAL EPIMERIZATION OF α,β-UNSATURATED γ-LACTONE
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N-Ethoxycarbonylmethyl Geissman-Waiss lactone ((+/-)-2) was easily synthesized from bis-lactone (3), and an unexpected epimerization of γ-butenolactone was observed in the process of asymmetric synthesis of 2.
- Tanaka, Masakazu,Murakami, Takeshi,Suemune, Hiroshi,Sakai, Kiyoshi
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p. 697 - 700
(2007/10/02)
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- The Shortest Synthesis of Optically Active Geissman-Waiss Lactone, A Key Synthetic Intermediate for Necine Bases
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A short synthesis of (+)-(1R,5R)-2-oxa-6-azabicyclooctan-3-one (the Geissman-Waiss lactone, 1) by palladium (II)-catalyzed intramolecular aminocarbonylation of (R)-N-benzyloxycarbonyl-3-hydroxy-4-pentenylamine (4) available from the Katsuki-Sharple
- Takahata, Hiroki,Banba, Yasunori,Momose, Takefumi
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p. 445 - 448
(2007/10/02)
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