Table 1. Structures and Y₁R Affinities (K_i Values) of Parent Compound 1a, Amine Precursors 8, 14, 15, Alkyne 39, and Fluorinated Argininamides 4, 7, 17–26, 28, 33–36, 38, and 41; Y₁R Antagonism (K_b Values) of 1a and Fluorinated Argininamides with a K_i below 100 nM; clogP Values of the Potential PET Ligands 4, 7, 17–26, 28, 33–36, 38, and 41 (Calculated with ACD/Labs 12.0 Using the Depicted Guanidine Tautomeric Form).

^aDissociation constant determined from the displacement of [³H]1b (K_d = 1.2 nM, c = 1.5 nM) on SK-N-MC cells; mean values ± SEM from at least two independent experiments each performed in triplicate.

^bInhibition of 10 nM pNPY induced [Ca²⁺]_i mobilization in HEL cells; mean values ± SEM from at least two independent experiments.

^cReported by Keller et al. 2011.²³

^dReported by Keller et al. 2008.²⁷

^eReported by Keller et al. 2011.²⁸

^fReported by Keller et al. 2013.²⁶

^gclogP value was calculated for the drawn structure.