5-Alkyl-2-(alkylthio)-6-(2,6-dihalophenylmethyl)-3,4-dihydropyrimidin-4( 3H)-ones: novel potent and selective dihydro-alkoxy-benzyl-oxopyrimidine derivatives.

Molecular modeling analysis of compounds belonging to the recently published series of dihydroalkoxy-benzyl-oxopyrimidines (DABOs), such as S-DABOs and DATNOs, gave support to the design of new 2,6-disubstituted benzyl-DABO derivatives as highly potent and specific inhibitors of the HIV-1 reverse transcriptase (RT). To follow up on the novel DABO derivatives, we decided to investigate the effect of electron-withdrawing substituents in the benzyl unit of the S-DABO skeleton versus their anti-HIV-1 activity. Such chemical modifications impacted the inhibitory activity, especially when two halogen units were introduced at positions 2 and 6 in the phenyl portion of the benzyl group bound to C-6 of the pyrimidine ring. Various 5-alkyl-2-(alkyl(or cycloalkyl)thio)-6-(2,B-dichloro(or 2, 6-difluoro)phenylmethyl)-3,4-dihydropyrimidin-4(3H)-ones were then synthesized and tested as anti-HIV-1 agents in both cell-based and enzyme (recombinant reverse transcriptase, rRT) assays. Among the various mono- and disubstituted phenyl derivatives, the most potent were those containing a 6-(2,6-difluorophenylmethyl) substituent (F-DABOs), which showed EC50's ranging between 40 and 90 nM and selectivity indexes up to greater than or equal to 5000. An excellent correlation was found between EC50 and IC50 values which confirmed that these compounds act as inhibitors of the HIV-1 RT. The structure-activity relationships of the newly synthesized pyrimidinones are presented herein.