Synthesis and Biological Evaluation of 5H-Indolo [3,2-b][1,5]Benzothiazepine Derivatives, Designed as Conformationally Constrained Analogues of the Human Immunodeficiency Virus Type 1 Reverse Transcriptase Inhibitor L-737,126

In the presence of sodium hydride, reaction of aryldisulphides with ethyl esters of indole-2-carboxylic acids furnished ethyl 3-arylthioindole-2-carboxy-lates, which were cyclized intramolecularly to afford 5 H-indolo[3,2-b][1,5]benzothiazepin-6(7 H)-ones or hydrolysed in alkaline medium to give 3-arylthioindole-2-carboxylic acids. These acids, also obtained by the action of aryldisulphides on indole-2-carboxylic acids, afforded tetracyclic 5 H-indolo [3,2-b][1,5]benzothiazepin-6(7 H)-ones upon treatment with EDCI–DMAP. Transformation of cyclic sulphides into the required sulphones was achieved by treatment with hydrogen peroxide or with m-chloroperbenzoic acid. The title derivatives are conformationally constrained analogues of the potent human immunodeficiency virus type 1 (HIV-1) reverse transcriptase inhibitor 3-benzene-sulphonyl-5-chloroindole-2-carboxamide (L-737, 126). Although the indolobenzothiazepine derivatives, as well as the indolyl aryl sulphones used for their synthesis, were endowed with anti-HIV-1 activities in the submicromolar and micromolar range, none of them proved more potent than L-737,126.