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2004
Pyridine derivatives
R 0380
Stereoselective Synthesis of Enantiomerically Pure Piperidine Derivatives by
of Pyridones. — 4-Pyridone (I) and 2-pyridone (X), bearing a
46- 139 N-Galactosylation
N-galactosyl group as chiral auxiliary, undergo highly regio- and stereoselective addition reactions with Grignard reagents to give 2-substituted and 4-substituted dehydropiperidinones, respectively. Prior to the addition step, activation of the pyridones by
O-silylation is necessary. The utility of (III) is demonstrated by synthesis of alkaloids
coniin (VI) and indolizine 167B (VII). Two strategies for the diastereoselective synthesis of cis-2,6-disubstituted 4-dehydropiperidinones, intermediates to alkaloid (VII), are
studied. However, in both cases disappointingly low diastereoselectivity is achieved.
— (KLEGRAF, E.; FOLLMANN, M.; SCHOLLMEYER, D.; KUNZ*, H.; Eur. J.
Org. Chem. 2004, 15, 3346-3360; Inst. Org. Chem., Johannes-Gutenberg-Univ.,
D-55128 Mainz, Germany; Eng.) — Klein
2004
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