Synthesis of potent lymphocyte function-associated antigen-1 inhibitors labeled with carbon-14 and deuterium, part 1

Abstract

The lymphocyte function-associated antigen-1 (LFA-1) is an essential component in normal immune system function and is a target for drug discovery for its broad therapeutic potential in treating inflammatory diseases. Here, we report the synthesis of three potent antagonists of LFA-1 labeled with carbon-14 and deuterium to support drug metabolism and pharmacokinetics studies. Carbon-14 labeled (R)-1-acetyl-5-(4-bromobenzyl)-3-(3,5-dichlorophenyl)-5-methyl-imidazolidine-2,4-dione (1) was prepared in 27% radiochemical yield in two steps and with a specific activity of 2.1 GBq/mmol by using [¹⁴C]-phosgene. Carbon-14 labeled 5-bromopyrimidine was used to prepare (R)-5-(1-piperazinylsulfonyl)-1-(3,5-dichlorophenyl)-3-[4-(5-pyrimidinyl)benzyl]-3-methyl-1-H-imidazo[1,2a]imidazol-2-one (2) and (R)-1-[7-(3,5-dichlorophenyl)-5-methyl-6-oxo-5-(4-pyrimidin-5-yl-benzyl)-6,7-dihydro-5H-imidazo[1,2-a]imidazole-3-sulfonyl]piperidin-4-carboxylic acid amide (3) via a Suzuki reaction with the corresponding boronic acid esters in 42% and 67% radiochemical yield and specific activities of 1.85 GBq/mmol and 1.95 GBq/mmol, respectively. Deuterium labeled piperazine was reacted with the sulfonyl chloride derivative (7), followed by a Suzuki coupling to the pyrimidine boronic ester to give deuterium labeled (2) in 47% yield. Deuterium labeled isonipecotamide was reacted in a similar way with the sulfonyl chloride derivative (14) to furnish deuterium labeled (3) in one step and in 94% yield. Copyright © 2011 John Wiley & Sons, Ltd.