Inspired by the synthetic and biological potential of organotellurium substances, a series of five- and six-membered ring organotelluranes containing a Te−O bond were synthesized and characterized. Theoretical calculations elucidated the mechanism for the oxidation-cyclization processes involved in the formation of the heterocycles, consistent with chlorine transfer to hydroxy telluride, followed by a cyclization step with simultaneous formation of the new Te−O bond and deprotonation of the OH group. Moreover, theoretical calculations also indicated anti-diastereoisomers to be major products for two chirality center–containing compounds. Antileishmanial assays against Leishmania amazonensis promastigotes disclosed 1,2λ 4-oxatellurane LQ50 (IC 50=4.1±1.0; SI=12), 1,2λ 4-oxatellurolane LQ04 (IC 50=7.0±1.3; SI=7) and 1,2λ 4-benzoxatellurole LQ56 (IC 50=5.7±0.3; SI=6) as more powerful and more selective compounds than the reference, being up to four times more active. A stability study supported by 125Te NMR analyses showed that these heterocycles do not suffer structural modifications in aqueous-organic media or at temperatures up to 65 °C.
- Te NMR spectroscopy
- oxidation–cyclization mechanism