The condensation of N-formyl-4-fluorophenylalanine (I) with 3-[bis(2-chloroethyl)amino]phenylalanine ethyl ester (II) by means of dicyclohexylcarbodiimide in THF gives N-formyl-4-fluoro-L-phenylalanyl-3-[bis(2-chloroethyl)amino]-L-phenylalanine ethyl ester (III), which is saponified with NaOH in DMF water yielding the free acid (IV). The condensation of (IV) with L-methionine ethyl ester (V) by means of N-hydroxysuccinimide and dicyclohexylcarbodiimide in DMF affords N-formyl-4-fluoro-L-phenylalanyl-3-[bis(2-chloroethyl)amino]phenylalanyl-L-methionine ethyl ester (VI), which is finally deprotected by elimination of the formyl group in ethanolic HCl.