3-(4-(6-Fluoroalkoxy-3,4-dihydroisoquinolin-2(1H)-yl)cyclohexyl)-1H-indole-5-carbonitriles for SERT imaging: chemical synthesis, evaluation in vitro and radiofluorination

Aminocyclohexyl indoles bind with high affinity and specificity toward the serotonin transporter (SERT). Based on this structural lead, we designed fluoroalkoxydihydroisoquinoline-cyclohexyl indole carbonitriles for future application as ¹⁸F-labeled tracers for SERT imaging by PET. Six compounds, three pairs of cis- and trans-isomer derivatives, respectively, were synthesized and evaluated in vitro. The chemistry of the new compounds, their affinity and specificity data, the general route to the phenolic precursor for labeling, and the successful ¹⁸F-fluoroalkylation of one pair of compounds are described herein.