Thiolates of arsenic(III) and Bi(III) with the anti-hypertensive drug captopril

Abstract

Arsenic trioxide, but not bismuth trioxide, reacted with the oral anti-hypertensive drug captopril giving the anhydrous (and in one case the dihydrated) tris(captoprilato)arsenic in good yields. Bismuth(III) nitrate pentahydrate reacted with 1, 2, 3 equivalents of captopril giving solutions containing the corresponding thiolato complexes and nitric acid. Their ¹H NMR spectra in CD₃OD showed that both major and minor captoprilato conformers existed and the more captoprilato ligands are coordinated to Bi(III) the more up field the CH₂S protons resonate. Addition of a calculated amounts of NaOH to the solutions of Bi(III)/captopril 1:1 and 1:2 gave solids insoluble in methanol or DMSO, the structures of which could not be reliably established by IR. The IR spectra of the isolated tris(captoprilato)arsenic and bismuth showed two νC = O bands for the COOH groups implying a complex hydrogen bonding network. These two complexes have sufficient solubility in water to be studied for biochemical or biological activities.