Synthesis and Anti-HIV-1 Activity of 2-[2-(3,5-Dimethylphenoxy)ethylthio]pyrimidin-4(3H)-ones

New 2-2-(3,5-dimethylphenoxy)ethyl]thio derivatives of pyrimidin-4(3H)-one containing various substituents at positions 5 and 6 of the pyrimidine ring were synthesized. It was shown that alkylation of 2-thiouracils with 1-bromo-2-(3,5-dimethylphenoxy)ethane in DMF takes place exclusively at the sulfur atom. The obtained 6-benzyl and 6-(2,6-difluorobenzyl) derivatives have clearly defined virus-inhibiting properties with respect to type 1 human immunodeficiency virus in vitro and suppress its reproduction by 50% at concentrations of 1.3 and 11.2 mM respectively.