Coupling of (3R,4R)-dimethyl-4-(3-hydroxyphenyl)piperidine (I) with N-Boc-L-valine (II) using benzotriazolyloxy-tris(dimethylamino)phosphonium hexafluorophosphate (BOP) provided amide (III). After deprotection of the Boc group of (III) with trifluoroacetic acid, the resulting valyl amide (IV) was reduced with BH3-Me2S to afford diamine (V). Finally, coupling of (V) with 3-(4-hydroxyphenyl)propionic acid (VI) in the presence of BOP yielded the target compound.