合成路线1

The reaction of L-phenylalanine (I) with benzyl bromide and K2CO3 in hot EtOH/H2O gives N,N,O-tribenzyl derivative (II), which is condensed with acetonitrile (III) by means of NaNH2 in THF yielding the pentanenitrile (IV). The reaction of nitrile (IV) with benzylmagnesium chloride (V) in THF affords the diphenylhexenone (VI), which is reduced with NaBH4 in THF to give the diphenylhexanol (VII) (slightly impurified (~10%) with other diastereomers that are not eliminated at this stage). The condensation of (VII) with acid chloride (VIII) (obtained by reaction of acid (IX) with SOCl2) in the presence of imidazole yields the amide (X), which is debenzylated with ammonium formate over Pd/C in methanol affording the amine (XI). At this stage the purification (elimination of the diastereomers) has been performed by crystallization of its salt with L-pyroglutamic acid (XII) in EtOH/DMF, pure salt (XIII) being obtained. Finally, this compound is condensed with the acid chloride (XIV) (obtained by reaction of acid (XV) with SOCl2) by means of NaHCO3 in ethyl acetate/water. The intermediates, the acids (IX) and (XV), have been obtained as indicated in schemes 24659001a and 24659001b (intermediates (XIII) and (X) of these schemes, respectively).

合成路线2