- A new synthesis of (2S)-4-oxopipecolic acid by thermal rearrangement of enantiopure spirocyclopropaneisoxazolidine
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A novel synthesis of (2S)-4-oxo-pipecolic acid is reported. The synthetic route employs as a key step the diastereoselective cycloaddition of the N- glycosylnitrone 7 to methylenecyclopropane followed by thermal rearrangement of the spirocyclopropaneisoxazolidine 8a. Stereoselective reduction of the N- BOC methyl ester of 4-oxopipecolic acid by L-selectride gives the protected cis-4-hydroxy-pipecolic acid 14.
- Machetti, Fabrizio,Cordero, Franca M.,De Sarlo, Francesco,Guarna, Antonio,Brandi, Alberto
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p. 4205 - 4208
(2007/10/03)
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- An Efficient Approach to the Family of 4-Substituted Pipecolic Acids. Syntheses of 4-Oxo-, cis-4-Hydroxy-, and trans-4-Hydroxy-L-pipecolic Acids from L-Aspartic Acid
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Syntheses of 4-oxo-, cis-4-hydroxy-, and trans-4-hydroxy-L-pipecolic acids from L-aspartic acid using hexafluoroacetone as protecting reagent are described.Combination of a Stille cross-coupling reaction with subsequent Lewis acid catalyzed intramolecular Michael addition provides 4-oxo-L-pipecolic acid 5 or trans-6-methyl-4-oxo-L-pipecolic acid.Borohydride reduction of the protected 4-oxo-L-pipecolic acid derivative gives the corresponding cis-4-hydroxy-L-pipecolic acid 8.The trans isomer 10 is obtained in good yield via Mitsunobu inversion. - Key words: 4-Oxo-L-pipecolic acid, 4-hydroxy-L-pipecolic acids, L-aspartic acid, hexafluoroacetone, intramolecular Michael addition, Stille reaction
- Golubev, Alexander,Sewald, Norbert,Burger, Klaus
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p. 2037 - 2040
(2007/10/02)
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