Synthesis and biodistribution of R- and S-isomers of [F-18]-fluoropropranolol, a lipophilic ligand for the beta-adrenergic receptor

The S and R isomers of [F-18] fluoropropranolol (1-[1-fluoro-2-isopropylami no]-3-naphthalen-1-yloxy-propan-2-ol) have been prepared by reductive alkyl ation of the appropriate aminoalcohols. The radiosynthesis provides a reaso nable yield (similar to 25%) to give products of 99% enantiomeric excess an d specific activities of 1-3 Ci/mu mol. The dissociation constants for the beta(2) adrenergic receptor are 0.5 and 2.5 nM for the S and the R isomers, respectively. The biodistribution data in rats show that uptake and egress of the tracer is rapid but that the result of blocking studies and the dif ference between the R and the S isomers suggest receptor-mediated uptake in receptor-rich tissue. (C) 2000 Elsevier Science Inc. All rights reserved.