2H-Pyrrol-2-one → HCID 67783663, compound

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Reaction Steps

A pyrrolone to act as a dienophile for cycloaddition to the triene 15 is prepared as follows. Methyl L-3-amino-(substituted phenyl)butyrate 16 is prepared from the appropriately substituted N-carbobenzoxy-L-alanine by Arndt-Eistert homologation, via the silver oxide-methanol rearrangement of the diazo ketone, followed by 10% Pd/C hydrogenolysis. The amino ester 16 is converted into the hydroxypyrrolone ester 17 by the method of Southwick, P. L., and R. T. Crouch, J. Am. Chem. Soc. 75:3413 (1953). The hydroxypyrrolone ester 17 is then treated with acetic anhydride-pyridine, with 4-N,N-dimethylaminopyridine as catalyst, for thirty minutes at room temperature, followed by hydrolysis-decarboxylation, using dimethyl sulfoxide-sodium chloride-water (50:28: 1), at 135°-140° C. for 1.5 hours in a nitrogen atmosphere. The liberated hydroxyl is then reacetylated, and the N-acetyl pyrrolone acetate 18 is isolated by chromatography on silica, using 4:1 hexane-ethyl acetate followed by 3:2 chloroform-ethyl acetate. ##STR6##

Provenance & Evidence