Synthesis and Anti-HIV-1 Activity of Novel 2,3-Dihydro-7H-thiazolo[3,2-a]pyrimidin-7-ones

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Abstract
Appropriately substituted 2,3-dihydro-7H-thiazolo[3,2-a]pyrimidin-7-ones 9−12 and 18 were considered as annulated analogues of HEPT (1-[(2-hydroxyethoxy)methyl]-6-(phenylthio)thymine), and some of these compounds were also found active against HIV-1, the most active one being 2,3-dihydro-5-[(3,5-dimethylphenyl)methyl]-3-ethoxy-6-ethyl-7H-thiazolo[3,2-a]pyrimidin-7-one (10b). S-Alkylation of 5-alkyl-6-(arylmethyl)-2-thiouracils 1−4 was performed with 2-bromoacetaldehyde acetals to furnish the S-[bis(alkoxy)ethyl] derivatives 5−8 and with allyl bromide to furnish S-allyl derivatives 17. The target compounds 9−12 were obtained by an N 1 regioselective intramolecular cyclization reaction of silylated 5−8 using trimethylsilyl trifluoromethanesulfonate (TMS triflate) as the catalyst. Treatment of the S-allyl derivatives 17 with bromine in dry methylene chloride afforded the 3-(bromomethyl) derivatives 18.