In continuation of our efforts to identify promising antileishmanial agents based on the chroman scaffold, we synthesized several substituted 2H-thiochroman derivatives, including thiochromenes, thichromanones and hydrazones substituted in C-2 or C-3 with carbonyl or carboxyl groups. Thirty-two compounds were thus obtained, characterized, and evaluated against intracellular amastigotes of Leishmania (V) panamensis. Twelve compounds were active, with EC50 values lower than 40 µM, but only four compounds displayed the highest antileishmanial activity, with EC50 values below 10 µM; these all compounds possess a good Selectivity Index > 2.6. Although two active compounds were thiochromenes, a clear structure-activity relationship was not detected since each active compound has a different substitution pattern.
As a part of our ongoing effort in the search for promising antileishmanial agents based on the thiochroman scaffold, we prepared a series of substituted 2H-thiochromenes. Thirty-three compounds were evaluated against intracellular amastigotes forms of L. (V) panamensis. Twelve compounds were active with EC50 values lower than 40 μM, and among those three compounds displayed the highest antileishmanial activity with EC50 values below 10 uM. Cytotoxicity was determined against human U-937 macrophages; thus, compounds having electrophilic alkenes (α,β-unsaturated carbonyl, or nitriles) displayed the highest antileishmanial activity but also moderate to high cytotoxicities. Based on SAR analysis, compounds 8d and 10, which differ only in the hydroxy group at C4, were selected as the most promising compounds in this library because good antiparasitic activity and Selectivity Index.
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