合成路线1

The reaction of 14C labeled chiral bromoacetyl sultam (I) with benzophenoneimine (II) in hot acetonitrile gives the substituted benzophenoneimine (III), which is estereoselectively alkylated with isopropyl iodide (IV) and n-BuLi in THF yielding the labeled L-valine derivative (V). The hydrolysis of (V) with HCl in THF affords the valine derivative (VI) with a free amino group that is protected with Boc2O in THF providing the carbamate (VII). The basic hydrolysis of (VII) with LiOH in THF gives the labeled N-(tert-butoxycarbonyl)-L-valine (VIII), which is esterified with Bn-OH, EDC and DMAP in dichloromethane yielding the protected benzyl ester (IX). Treatment of (IX) with TFA in dichloromethane affords L-valine benzyl ester (X), which is condensed with the bromomethylbiphenyl (XI) by means of DIEA in hot DMF to give the N-alkylated valine ester (XII). The acylation of (XII) with pentanoyl chloride (XIII) by means of DIEA in toluene yields the N-disubstituted valine ester (XIV), which is finally deprotected by hydrogenation with H2 over Pd/C in EtOH.