Synthesis of novel thiazolothiazapine based HIV-1 integrase inhibitors

Thiazolothiazepines are among the smallest and most constrained inhibitors of human immunodeficiency virus type-1integrase (HIV-1 IN) inhibitors (J. Med. Chem. 1999, 42, 3334). Previously, we identified two thiazolothiazepines lead IN inhibitorswith antiviral activity in cell-based assays. Structural optimization of these molecules necessitated the design of easily synthesizableanalogs. In order to design similar molecules with least number of substituent, herein we report the synthesis of 10 novel analogs.One of the new compounds (1) exhibited similar potency as the reference compounds, confirming that a thiazepinedione fused to anaphthalene ring system is the best combination for the molecule to accommodate into the IN active site. Thus, the replacement ofsulfur in the thiazole ring with an oxygen does not seem considerably affect potency. On the other hand, the introduction of an extramethyl group at position 1 of the polycyclic system or the shift from a thiazepine to an oxazepine skeleton decreased potency. Inorder to understand their mode of interactions with IN active site, we docked all the compounds onto the previously reported X-raycrystal structure of IN. We observed that compounds 7–9 occupied an area close to D64 and Mg2þ and surrounded by amino acidresidues K159, K156, N155, E152, D116, H67, and T66. The oxygen atom of the oxazolo ring of 7 and 8 could chelate Mg2þ. Theseresults indicate that the new analogs potentially interact with the highly conserved residues important for IN catalytic activities.