The condensation of ethyl 2-[4-[2-(heptylamino)ethyl]phenoxy]-2-methylpropionate (XIII) with 4-fluorophenyl isocyanate (XI) gives the corresponding ureido compound (XIV), which is then hydrolyzed with NaOH in refluxing ethanol.
The N-protection of 4-(2-aminoethyl)phenol (I) with benzyl chloroformate gives the N-benzyloxycarbonyl derivative (II), which is condensed with 1-methyl-1-(trichloromethyl)ethanol (III) by means of NaOH in acetone yielding the phenoxyisobutyric acid (IV). The deprotection of the amino group of (IV) by hydrogenation over Pd/C affords the ethylamino derivative (V), which is reprotected with 9-fluorenylmethoxycarbonyl protecting group to provide carbamate (VI). The acid group of (VI) is then coupled to a Sasrin polystyrene resin giving the N-protected resin (VII), which is deprotected with piperidine affording resin (VIII) with a free amino group, which is condensed with heptanoic acid (A) by means of DIC and HOBT to give the amide (IX). The reduction of the carbonyl group amide (IX) with BH3/THF yields the heptylamine (X), which is condensed with 4-fluorophenyl isocyanate (XI) to afford the urea (XII). Finally, this compound is treated with trifluoroacetic acid to eliminate the polystyrene resin and isolate the target compound. Alternatively, the heptylamine (X) can also be obtained directly by reductocondensation of the free amino group of the resin (VIII) with heptanal (B) by means of NaBH3CN.