With the rapid development and complex challenges of chemical substances, new drug synthesis pathways are usually the most effective.325145-35-5,(S)-tert-Butyl 2-ethylpiperazine-1-carboxylate,as a common compound, the synthetic route is as follows.
ER-895473 (103 mg, 0.261 mmol, 27.1percent yield) was prepared in a similar manner to ER-899742 starting with 38 (286 mg, 0.962 mmol) and (S)-tert-butyl 2-ethylpiperazine-1-carboxylate (206 mg, 0.962 mmol). DMF (3 mL) was used instead of DCM for the amide forming reaction and 2.0 M HCl in ethyl ether (1.3 mL, 2.6 mmol) was used in the Boc-deprotection process using acetonitrile (1 mL) as a solvent. ER-895473 was purified by reverse-phase HPLC (X-Bridge C18 19×100 mm column; eluting with a gradient of increasing acetonitrile in water containing 0.1percent formic acid). The product fractions were combined and concentrated to dry followed by dilution in MeOH (1 mL), passed through as basic silica gel plug (Biotage SiCO3, 1 g, eluting with MeOH (1 mL)), concentrated and dried in vacuo.To a stirred solution of 38 (300 mg, 1.01 mmol) in DCM (2 mL) was added the mixture of (3S,4R)-tert-butyl 3-amino-4-fluoropyrrolidine-1-carboxylate and (3R,4S)-tert-butyl 3-amino-4-fluoropyrrolidine-1-carboxylate, 77 (205.3 mg, 1.005 mmol), HBTU (247 mg, 1.211 mmol) and DIEA (0.70 mL, 4.04 mmol) followed by stifling at rt for 16 h. The was found complete and concentrated to dryness followed by dissolving in EtOAc (20 mL), washed 1 time with water (10 mL), 2 N citric acid in water (10 mL), saturated NaHCO3 (10 mL), and brine (10 mL). The combined aqueous layers were extracted 3 times with EtOAc (10 mL ea.) after which time the combined organic fractions were dried over MgSO4, filtered and concentrated to dry. The crude product was purified over a 25 g Biotage silica gel column eluting with 0-10percent MeOH in DCM (200 mL total) to provide the diastereomeric mixture of 78 and 79., 325145-35-5
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Reference：
Patent; CARLSON, ERIC; HANSEN, HANS; HAWKINS, LYNN; ISHIZAKA, SALLY; MACKEY, MATTHEW; SCHILLER, SHAWN; OGAWA, CHIKAKO; DAVIS, HEATHER; US2015/105370; (2015); A1;,
Piperazine – Wikipedia
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