2002 diastereoselective syntheses, enantioselective syntheses

diastereoselective syntheses, enantioselective syntheses (incl. cis/trans-isomerism)O 0031

52 - 030Diastereoselective Synthesis and Estimation of the ConformationalFlexibility of 6-Oxoperhydropyridazine-3-carboxylic Acid Derivatives.— Readily available α,β-didehydroglutamate derivatives such as (III) and (IX)are transformed via tetrahydropyridazinones into the corresponding target per-hydropyridazinones by reduction of the imino bond employing NaCNBH3. Thediastereoselectivity of this reduction is controlled by the substituent at C-4 of thepyridazinone ring. 4-Substituted pyridazinone derivatives give rise to high 3,4-cisdiastereoselectivities irrespective of the 4,5-stereochemistry, whereas only 20%d.e. are found for 4-unsubstituted pyridazinone derivatives. 4,5-Disubstitutedtetrahydropyridazinones can be prepared in both 4,5-cis and 4,5-trans fashionby the appropriate choice of method. — (ALVAREZ-IBARRA, CARLOS;CSAKY, AURELIO G.; GOMEZ DE LA OLIVA, CRISTINA; J. Org. Chem.67 (2002) 9, 2789-2797; Dep. Quim. Org., Fac. Quim., Univ. Complutense,E-28040 Madrid, Spain; EN)

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2002 diastereoselective syntheses, enantioselective syntheses

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