Efficient synthesis of the pyrimidine TIBO analog 3, starting from 9-benzyl-6-chloropurine and testing of its ability to inhibit the replication of the HIV-1 virus in MT-4 cells are described. We have reported that members of a novel series of tetrahydro-imidazo[4,5,1-ik][1,4]-benzodiazepin-2(1H)one and -thione (TIBO), such as 1 and 2, inhibit the replication of HIV-1 [1,2] (the main etiological agent of AIDS), but not of HIV-2, or of any other DNA or RNA viruses tested to date [3-5]. The unprecedented specificity of these compounds is believed to result from an interaction with reverse transcriptase, the unique viral enzyme responsible for translation of HIV-1 viral RNA into DNA which is incorporated into host cells' genomic DNA. Previous studies have established that 2 inhibits the isolated reverse transcriptase [6]. In laboratory tests, TIBO derivatives inhibited reproduction of the HIV-1 virus at concentrations far below those toxic to uninfected cells. Compound 2 is currently being evaluated in clinical trials as another drug to add to anti-AIDS therapy. In the course of SAR studies to find even more potent analogs, phenyl substituents were varied and those studies will be published in the future. Additionally, substitution of heteroaromatics for the benzo portion of the TIBO structure was undertaken. This report describes the synthesis and anti-HIV-1 testing result of pyrimidine analog 3, an example of that type of change.