p-Toluenesulfonic acid → (S,Z)-3-[(5-tert-Butyloxazol-4-yl)methylene]-6-benzylpiperazine-2,5-dione

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Reaction Steps

Using a Deanstark trap, a solution of compound 4 (50 mg, 0.14 mmol) in toluene was refluxed in the presence of p-toluenesulfonic acid (0.8 mg, 3 mol %) for 18 h. After solvent was removed in vacuo, the residue was purified by preparative HPLC (μBondasphere 5C18 100 A, 19×150 mm) and eluted using a linear gradient from 40 to 60% CH3CN in 0.1% TFA aq over 40 min at a flow rate of 5 mL/min, and the desired fraction was collected and lyophilized to obtain KPU-245; yield 11 mg (23%); m.p. 52-56° C., 1H NMR (300 MHz, DMSO-d6) δ 10.65 (s, 1H), 8.60 (s, 1H), 8.47 (s, 1H), 7.24-7.13 (m, 5H), 6.37 (s, 1H), 4.52 (br s, 1H), 3.20 (dd, J=3.7, 13.6 Hz, 1H), 2.95 (dd, J=5.0, 13.6 Hz, 1H), 1.31 (s, 9H); HRMS (EI): m/z 339.1584 (M+) (calcd for C19H21N3O3: 339.1583).

Provenance & Evidence