Cyclohexyl isocyanate → Ethyl(({1-[(cyclohexylamino)carbonyl]piperidin-4-yl}methyl){4-[(dodecylamino)carbonyl]benzyl}amino)(oxo)acetate

The resin-bound ethyl[{4-[(dodecylamino)carbonyl]benzyl}(piperidin-4-ylmethyl)amino]-(oxo)acetate (described in step h, 0.0426 mmol) was swelled in THF (0.5 mL) for 15 min at rt. Cyclohexyl isocyanate (18 mg, 0.143 mmol) dissolved in THF (0.9 mL) and TEA (29 mg, 0.282 mmol) was added and the reaction mixture was shaken 14 h at rt. The resin was washed successively with THF (1×0.15 min), MeOH (1×15 min), THF (1×15 min), MeOH (3×10 min), DMF (3×10 min), MeOH (1×5 min), THF (3×10 min), MeOH (1×5 min), DCM (3×10 min) and with Et2O (1×10 min). The resin was then dried under vacuum to afford the title compound which was used directly in the next step.