Detection of hard electrophilic reactive metabolites formed from alicyclic amines using glutathione trapping

Alicyclic amines are ubiquitous compounds with manifold uses in medicinal chemistry. Unfortunately, they are subject to metabolic activation to form reactive intermediates. Alicyclic amines were observed to form direct cysteine (Cys) or cysteinylglycine (CysGly) conjugates across a large GSK GSH trapping dataset. These results suggest that hard electrophilic intermediates were generated from the alicyclic amines (e.g. piperidine) and trapped as Cys and/or CysGly conjugates. This is unusual since there is a general consensus that alicyclic amine biotransformation forms hard electrophiles typically require hard nucleophile trapping agents and cannot be trapped by soft nucleophiles.Compound A and tofacitinib, both containing a piperidine group, were used as alicyclic amine examples to explore the bioactivation pathways generating hard electrophiles in GSH trapping studies. Direct Cys and CysGly conjugates on the piperidine ring were observed for Compound A and tofacitinib in GSH trapping experiments. Both were proposed to be the thioethers resulting from reactions with hard electrophile iminium intermediates. Aldehyde intermediates formed through piperidine ring-opening were also captured by Cys and CysGly. Therefore, the aforementioned hard electrophiles created through bioactivation of alicyclic amines can be screened in drug discovery GSH trapping studies.