Oxidative Ring-Opening of rel-(2R,3R,5S)-5-Aryl-2-benzoylamino-6,7-bis(methoxycarbonyl)-2,3-dihydro-1-oxo-3-phenyl-1H,5H-pyrazolo1,2-a-pyrazoles. Synthesis of rel-(2R,3R)-3-Phenyl-3-5-aryl-3,4-bis(methoxycarbonyl)pyrazolyl-1ananine Esters

摘要

rel-(2R,3R)-N-Benzoylamino-6,7-bis(methoxycarbonyl)-2,3-dihydro-1-oxo-1H,5H-pyrazolo1,2-a-pyrazoles 5, accesible by cycloaddition of dimethyl acetylenedicarboxylate (3) to (1Z)-rel-(4R,5R)-1-aryl-methylidene-4-benzoylamino-5-phenyl-3-pyrazolidinone-1-azomethine imines 4, undergo oxidative ring cleavage with methanolic bromine giving rel-(2R,3R)-N-benzoyl-3-phenyl-3-5-aryl-3,4-bis(methoxycarbonyl)pyrazolyl-1alanine methyl esters 6 as products.