Synthesis and Potent Anti-HIV-1 Activity of Novel 6-Benzyluracil Analogues of 1-[(2-Hydroxyethoxy)methyl]-6-(phenylthio)thymine

Ethyl 2-alkyl-4-aryl-3-oxobutyrates were synthesized from the corresponding arylacetonitriles and 2-bromo esters. Condensation of the butyrates with thiourea followed by treatment with chloroacetic acid afforded the 5-alkyl-6-(arylmethyl)uracils. Condensation of the uracils with acetals using trimethylsilyl triflate (TMS triflate) as a catalyst gave acyclic 5-alkyl-6-(arylmethyl)uracil derivatives. 6-Benzyl-5-ethyluracil was also condensed with methyl 5-O-(tert-butyldiphenylsilyl)-2-deoxy-3-O-(phenoxythiocarbonyl)-α,β-d-erythro-pentofuranoside, followed by Barton reduction and deprotection, to give the anomers of 6-benzyl-5-ethyl-2‘,3‘-dideoxyuridine. Alkylation of the uracils with alkyl chloromethyl sulfides gave new thio analogues of HEPT. All new N -substituted uracils were tested for activity against HIV-1, and the thio analogues were found extremely potent.