Synthesis of chromenochalcones and evaluation of their in vitro antileishmanial activity

A large number of novel chromenochalcones were synthesized by pyridine-catalysed chromenylation of mono-chelated meta-dihydric acetophenones with the monoterpene, citral dimethyl acetal and subsequent Claisen-Schmidt condensation of the resultant acylchromenes with appropriate aromatic aldehydes. These chromenochalcones 1-19 were screened against in vitro extracellular promastigotes and intracellular amastigotes of Leishmania donovani. The most potent compound in this series was compound 9 with a pyridine ring-A, which showed 99% inhibition of promastigotes at 10 microg/ml, 82% at 0.25 microg/ml and 96% at 10 microg/ml concentration against amastigotes.