Late‐Stage Diversification of Pyrazoles as Antileishmanial Agents

Abstract

AbstractN‐Pyrazolylcarboxamides and N‐pyrazolylureas represent promising lead compounds for the development of novel antileishmanial drugs. Herein, we report the late‐stage diversification of 3‐bromopyrazoles 10 A/B and 14 A by Pd‐catalyzed Sonogashira and Suzuki‐Miyaura cross coupling reactions. The electron‐withdrawing properties of the cyano moiety in 4‐position of the pyrazole ring limited the acylation of the primary amino moiety in 5‐position. A large set of pyrazoles bearing diverse aryl and alkynyl substituents in 3‐position was prepared and the antileishmanial and antitrypanosomal activity was recorded. The urea 38 lacking the electron withdrawing cyano moiety in 4‐position and containing the large 4‐benzylpiperidinoo moiety exhibited a modest antileishmanial (IC50=19 μM) and antitrypanosomal activity (IC50=7.9 μM)). However, its considerable toxicity against the PMM and MRC‐5 cells indicates low selectivity, i. e. a small gap between the desired antiparasitic activity and undesired cytotoxicity of <2‐ to 4‐fold.