Diisopropylethylamine → (3R*,5S*)-3-tert-Butoxycarbonylamino-5-[(2-chloro-benzyl)-cyclopropylcarbamoyl]-piperidine-1-carboxylic acid 9H-fluoren-9-ylmethyl ester

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Reaction Steps

To a stirred, ice-cooled mixture of (3S*,5R*)-5-tert-butoxycarbonylamino-piperidine-1,3-dicarboxylic acid 1-(9H-fluoren-9-ylmethyl) ester (233.3 mg, 0.5 mmol), (2-chlorobenzyl)-cyclopropylamine (99.9 mg, 0.55 mmol) and N-ethyldiisopropylamine (685 μL, 4 mmol) in dimethylacetamide (2.5 mL), propylphosphonic anhydride solution (˜50% in DMF, 480 μL, ˜0.75 mmol) is added. The reaction mixture is stirred for 14 h at RT, diluted with ethyl acetate and washed twice with an aqueous NaHCO3 solution. The combined organic layers are dried (Na2SO4) and evaporated in vacuo, and the residue is purified by preparative HPLC (C18 column, 10-100% CH3CN+0.1% TFA/H2O+0.1% TFA, 20 min, flow 20 mL/min). The combined pure fractions are treated with Na2CO3, CH3CN is removed in vacuo, and the residual aqueous phase is extracted three times with CH2Cl2. The combined organic layers are dried (Na2SO4) and evaporated to afford the title compound as a white amorphous solid. MS: 630.7 [M+H]+; tR (HPLC, Nucleosil C18; 5-100% CH3CN+0.1% TFA/H2O+0.1% TFA for 8 min, then 100% CH3CN+0.1% TFA for 2 min, flow 1.5 ml/min): 8.24 min.

Provenance & Evidence