(4-Formyl-cyclohexylmethyl)-carbamic acid tert-butyl ester (390 mg, 1.6 mmol) and (S)-amino-phenyl-acetic acid cyclopentyl ester (394 mg, 1.8 mmol) were stirred in DCE (6 ml) at r.t. for 25 min. Acetic acid (9.6 ul, 0.16 mmol) and sodium triacetoxy-borohydride (1.0 g, 4.8 mmol) were added and the resulting mixture was stirred for 1 h30 at r.t. DCM (10 ml) and a saturated solution of NaHCO3 (10 ml) were added and phases were separated. Aqueous were extracted with EtOAc (2×10 ml), the organics were dried over magnesium sulfate, filtered and evaporated to dryness. The crude product was purified by column chromatography (8:2 heptane/EtOAc) to yield 223 mg of the pure amine (31% yield). LCMS purity 100%, m/z 445 [M++H]+.
