Inherently Chiral 2,2’-biindole Oligomer Films for the Enantioselection of Chiral Active Pharmaceutical Ingredients, including a Real Matrix.

Chirality and chiral analysis constitute a key aspect of modern chemistry and chemical technologies; the enantiomeric purity of various compounds is important in different fields, especially in the pharmaceutical one [1-3]. A systematic study case is proposed, based on a new 2,2'-biindole series (N-alkyl-IND)2Ph2T4 (alkyl= methyl, propyl or hexyl group), featuring systematic variation of the N alkyl substituents of the pyrrolic rings in the core. The new series shows good performances when applied as selectors in chiral voltammetry for discrimination of the enantiomers of model chiral ferrocenyl probes, either in CH2Cl2, by conversion into enantiopure electroactive electrode surfaces by electrooligomerization on glassy carbon substrate or in achiral ionic liquid BMIMTf2, as chiral additive (monomer with hexyl chains, which hamper electrooligomerization). Discrimination is conveniently and reproducibly achieved in terms of significant potential differences for the two enantiomers, specularly inverting either probe or selector configuration. In one case successful discrimination is even observed with the two probe enantiomers concurrently present, either as racemate or with enantiomeric excesses, neatly accounted for by the peak current ratios. Oligo-(N-Me-IND)2Ph2T4 films also result in enantiomer discrimination for quite different chiral probes, active pharmaceutical ingredients: terazosin, lansoprazole, ramosetron and clopidogrel, working in aqueous buffer. Moreover, the molecule (S)-clopidogrel was also tested in a real matrix, i.e. as the main component of the DuoPlavin®, drug in combination with acetylsalicylic acid (both active substances are antiplatelet medicines). This work confirms the wide-scope effectiveness of the new inherently chiral selectors and suggesting application to a wider pool of chiral probes of applicative interest.