Synthesis, reactions, and preliminary evaluations of enaminone esters

The objective of this work was to design enaminone esters that would possess potential medicinal properties. The reaction between beta-hydroxyketo esters and primary or secondary amines yielded secondary or tertiary enaminone esters, respectively. The UV spectra of the enaminone esters were determined in acidic, alkaline, and neutral media; the spectra have a hypsochromic shift in acidic media in comparison with neutral media. The enaminone esters provided nucleophilic and electrophilic sites for a variety of reactions. Thus, the enaminone esters were converted into enaminone amides and O-alkylation products exclusively. Although the enaminone esters were generally resistant to reduction by metal hydrides, one unhindered enaminone ester was reduced to an alcohol with sodium borohydride. Another enaminone ester reacted with guanidine to give the corresponding quinazolinone. Due to the variety of nucleophilic and electrophilic sites in the enaminone system, enaminone esters possess a great potential as reaction intermediates and medicinal compounds. Preliminary evaluations of the enaminone esters revealed a histaminergic effect, uterine relaxant properties, and anticonvulsant activity.