The above prepared 3-methanesulfonyloxy-benzoic acid (0.400 g, 1.85 mmol) was condensed with 4-amino-1-BOC-piperidine (0.370 g, 1 eq.) in the presence of 1.1 eq. of (benzotriazol-1-yloxy)-tris-(dimethylamino)phosphonium hexafluorophosphate (0.899 g) and 1.2 eq. of N-ethyl-diisopropylamine (0.38 ml) in 9 ml of abs. THF during one night at ambient temperature. Pouring onto crashed ice/AcOEt, twofold extraction with AcOEt, washing with water, drying over sodium sulfate, and evaporation of the solvents, followed by flash chromatography (SiO2, hexane/AcOEt=7/3), yielded 0.920 g of the title compound as white foam, contaminated with some reagent derived impurities, but sufficiently pure for the next steps.
