Easy Synthesis of 5,6-Disubstituted Acyclouridine Derivatives

Abstract

Ethyl 2-ethyl-3-oxo-4-phenylbutyrate is synthesized in a high yield from the corresponding benzyl cyanide and ethyl 2-bromobutyrate or by reaction of the potassium salt of ethyl 2-ethylmalonate with phenylacetyl chloride. Condensation of the 3-oxo ester with thiourea, desulfurization with chloroacetic acid and finally condensation with acetals or 1,3-dioxolanes using trimethylsilyl triflate (TMS triflate) as a catalyst or with chloromethyl ethyl ether afforded the 5-ethyl-6-benzyl acyclouridine derivatives.