A convergent approach to the synthesis of aprepitant: a potent human NK-1 receptor antagonist

A simple and convergent approach to enantiomerically pure 5-[[2-[1-[3,5-bis(trifluoromethyl)phenyl]ethoxy-3-(4-fluorophenyl)morpholin-4-yl]methyl]-1,2-dihydro-1,2,4-triazol-3-one 1, a potent orally active antagonist of the human neurokinin-1 (NK-1) receptor, is described. The synthetic procedure starts from p-fluorobenzaldehyde to access the racemic morpholinone 2 via a modified Strecker synthesis and utilizes a diastereomeric salt resolution technique to accomplish the synthesis of 1 in enantiomerically pure form and good yield.