- A TOTAL SYNTHESIS OF (+/-)-INTEGERRIMINE
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A total synthesis of a 12-membered bislactonic pyrrolizidine alkaloid, integerrimine, has been achieved.
- Narasaka, Koichi,Sakakura, Toshiyasu,Uchimaru, Tadafumi,Morimoto, Kiyoshi,Mukaiyama, Teruaki
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- Identification of senecionine and senecionine N-oxide as antifertility constituents in Senecio vulgaris
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The MeOH extract of Senecio vulgaris L., administered po to rats on Days 1-10 postcoitum, significantly decreased the number of normal fetuses per pregnant rat found at autopsy on Day 16. Additional experiments showed a similar activity for its hepatotoxic constituents senecionine and senecionine N-oxide, suggesting that the latter two compounds were probably responsible for the effect seen with the extract. No antifertility effects were seen in MeOH extract-treated hamsters.
- Tu,Konno,Soejarto,Waller,Bingel,Molyneux,Edgar,Cordell,Fong
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- A synthesis of senecionine, a representative of hepatoxic, macrocyclic pyrrolizidine alkaloids of retronecine type
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Described is a synthesis of (-)-senecionine, the best-known hepatoxic, 12-membered pyrrolizidine alkaloid of retronecine type. Integerrinecic acid lactone methyl ester was converted into protected senecic acid, which was regioselectively coupled with (+)-retronecine, achieving the first synthesis of (-)-senecionine.
- Niwa,Sakata,Yamada
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- Stereoselective Synthesis of the Pyrrolizidine Alkaloids (-)-Integerrimine and (+)-Usaramine
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Two routes to the pyrrolizidine alkaloid (-)-integerrimine (1) are described.The first, starting from methyl (R)-(-)-3-hydroxy-2-methylpropionate, proceeded in 19 steps to integerrinecic acid lactone (5) which was transformed to the necic acid derivative 30.The latter was coupled to protected retronecine 31, and the synthesis of 1 was completed by lactonization employing Vedejs' protocol.A second, shorter synthesis of (-)-1 was accomplished via 5, starting from (R)-(+)-β-citronellol (36).This pathway invoked Katsuki-Sharpless epoxidation of 42 for stereoselective construction of the tertiary alcohol of integerrinecic acid.A parallel sequence proceeding via the stereoisomeric epoxide 44 led to the necic acid segment 75 of the alkaloid (+)-usaramine (2).This acid was coupled to the retronecine borane 82 and then lactonized to 2.
- White, James D.,Amedio, John C.,Gut, Samuel,Ohira, Susumu,Jayasinghe, Lalith R.
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p. 2270 - 2284
(2007/10/02)
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- Total Synthesis of Optically Active Integerrimine, a Twelve-membered Dilactonic Pyrrolizidine Alkaloid of Retronecine Type
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A total synthesis of the natural enantiomer of integerrimine (1), a twelve-membered dilactonic pyrrolizidine alkaloid of retronecine type has been achieved through the enantioselective synthesis and regioselective coupling of (+)-retronecine (4) and (+)-integerrinecic acid (methylthio)methyl ether (6).
- Niwa, Haruki,Miyachi, Yasuyoshi,Okamoto, Osamu,Uosaki, Youichi,Kuroda, Akio,et al.
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p. 393 - 412
(2007/10/02)
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- Total Synthesis of a Macrocyclic Pyrrolizidine Alkaloid, (+/-)-Integerrimine, Utilizing an Activable Protecting Group
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A new esterification reaction has been developed utilizing a (methylthio)methyl (MTM) group as an activable protecting group of carbocyclic acid.A total synthesis of a 12-membered pyrrolizidine alkaloid, (+/-)-integerrimine (1), has been achieved by applying the above method to formation of the macrocyclic bislactone skeleton.The acid anhydride (16b) of the integerrinecic acid derivative was coupled with lithium alkoxide of retronecine silyl ether (5b) in the presence of DMAP to afford the α,β-unsaturated ester.Oxidation of the MTM group afforded an active (methylsulfonyl)methyl ester (28b), which cyclized to give the macrocyclic bislactone 29.
- Narasaka, Koichi,Sakakura, Toshiyasu,Uchimaru, Tadafumi,Guedin-Vuong, Denis
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p. 2954 - 2961
(2007/10/02)
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