A racemic imidazolidinone (1-tert-butoxycarbonyl-2-tert-butyl-3-methyl-4-imidazolidinone) has been subjected to kinetic resolution using a homochiral lithium amide base [lithium (R,R)-bis(1-phenylethyl)amide], thus enabling access to the optically active material in up to 80 % enantiomeric excess.