Novel substituted N-benzyl(oxotriazinoindole) inhibitors of aldose reductase exploiting ALR2 unoccupied interactive pocket

[Display omitted] •Four novel aldose reductase inhibitors exploiting an unoccupied enzyme pocket were developed.•All novel inhibitors revealed higher inhibitory efficacy and selectivity compared to their lead.•Additional inhibitor-enzyme interactions were suggested to be responsible for the improved biological activity.•Based on this study, several novel promising derivatives were proposed. Recently we have developed novel oxotriazinoindole inhibitors (OTIs) of aldose reductase (ALR2), characterized by high efficacy and selectivity. Herein we describe novel OTI derivatives design of which is based on implementation of additional intermolecular interactions within an unoccupied pocket of the ALR2 enzyme. Four novel derivatives, OTI-(7–10), of the previously developed N-benzyl(oxotriazinoindole) inhibitor OTI-6 were synthetized and screened. All of them revealed 2 to 6 times higher ALR2 inhibitory efficacy when compared to their non-substituted lead compound OTI-6. Moreover, the most efficient ALR2 inhibitor OTI-7 (IC50 = 76 nM) possesses remarkably high inhibition selectivity (SF ≥ 1300) in relation to structurally related aldehyde reductase (ALR1). Derivatives OTI-(8–10) bearing the substituents –CONH2, –COOH and –CH2OH, possess 2–3 times lower inhibitory efficacy compared to OTI-7, but better than the reference inhibitor OTI-6. Desolvation penalty is suggested as a possible factor responsible for the drop in ALR2 inhibitory efficacy observed for derivatives OTI-(8–10) in comparison to OTI-7.