Multiple labeling of a potent CX 3 CR1 antagonist for the treatment of multiple sclerosis

Several methods for the preparation of five isotopologues of the CX 3 CR1 antagonist 1 were developed. Volatile and radioactive 1‐chloro‐ and 1‐bromo‐ethyl‐benzene was handled in [2′‐ 14 C] and [3′, 5′‐ 3 H] labeling of 1. d ‐Leucinol (( R )‐2‐amino‐4‐methylpentan‐1‐ol) was labeled as [1‐ 14 C] and [4‐ 14 C] via a Wittig reaction using Garner's aldehyde and a Strecker amino acid synthesis with d ‐acylase resolvation, respectively. A [ 2 H 10 ] d ‐leucinol was used for the stable labeled [M + 10] isotopologue. The products were isolated with 97.6–100% stereo chemical and radiochemical purity as for specific activity 768 GBq/mmol and 1.6–2.0 GBq/mmol, respectively.