- Amino Acids. 7. A Novel Synthetic Route to L-Proline
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Reaction of L-5-oxoproline esters L-2 with phosgene at 0 deg C gives L-5,5-dichloro-1-(chlorocarbonyl)proline esters L-6, which readily lose hydrogen chloride to form L-5-chloro-1-(chlorocarbonyl)-4,5-dehydroproline esters L-7.Catalytic hydrogenation (Pd/C, 180 bar) of L-7 yields L-1-(chlorocarbonyl)proline esters L-15 and thence, upon hydrolysis, L-proline (L-17).A 'one-pot reaction' for the whole sequence is described, starting from easily accessible L-5-oxoproline esters and yielding L-proline in 78percent overall yield and 99.7percent optical purity.
- Drauz, Karlheinz,Kleemann, Axel,Martens, Juergen,Scherberich, Paul,Effenberger, Franz
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p. 3494 - 3498
(2007/10/02)
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- Process for the production of L-proline
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L-proline is produced from the methyl or ethyl ester of L-pyroglutamic acid by reacting this with at least twice the molar amount of phosgene to form the corresponding 1-chlorocarbonyl-5,5-dichloroproline ester, producing the corresponding 2-chloro-1-chlorocarbonyl-pyrrolin-(2)-carboxylic acid ester-(5) therefrom by splitting off hydrogen chloride, catalytically hydrogenating the pyrrolin-(2) compound to the corresponding N-chlorocarbonyl-proline ester and hydrolyzing the latter with acid to form L-proline.
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