Structural Modification of the Designer Stimulant α-Pyrrolidinovalerophenone (α-PVP) Influences Potency at Dopamine Transporters

alpha-Pyrrolidinovalerophenone (alpha-PVP, 7) is an illegal synthetic stimulant that is being sold on the clandestine market as flakka and gravel. The potent pharmacological effects of alpha-PVP are presumably mediated by inhibition of dopamine uptake at the dopamine transporter (DAT). However, little is known about how structural modification of alpha-PVP influences activity at DAT. Eleven analogs of alpha-PVP were synthesized and examined for their ability to inhibit uptake of [H-3]clopamine and [H-3]serotonin in rat brain synaptosomes. None of the analogs significantly inhibited [H-3]serotonin uptake when tested at 10 mu M at the serotonin transporter (SERT). All of the analogs behaved as DAT reuptake inhibitors, but potencies varied over a >1500-fold range. Potency was primarily associated with the nature of the alpha-substituent, with the more bulky substituents imparting the highest potency. Expansion of the pyrrolidine ring to a piperidine reduced potency up to 10-fold, whereas conformational constraint in the form of an aminotetralone resulted in the least potent compound. Our study provides the first systematic and comparative structure activity investigation on the ability of alpha-PVP analogs to act as inhibitors of DAT.