To a solution of 4-methylmorpholine-2,6-dione (1 eq) (see for Ref. WO 03/093261) in toluene (0.06 M) was added N2 (Example 14, step 2). The reaction mixture was refluxed for 2 h and then allowed to stand at RT overnight. The solvent was removed under reduced pressure. The resulting crude was dissolved in DMF (0.2 M) and to the resulting solution were added sequentially TBTU (1.3 eq), DIPEA (2.2 eq) and DMAP (0.3 eq). The mixture was stirred at RT for 2 h and then the product was isolated by purification at prep RP-HPLC using H2O (+0.1% TFA) and MeCN (+0.1% TFA) as eluents (C18 column). The desired fractions were lyophilized to afford the desired compound as a white powder. 1H NMR (400 MHz, DMSO-d6+TFA) δ: 7.41-7.27 (2H, m), 7.14 (1H, s), 7.08 (1H, d, J=6.8 Hz), 6.59 (1H, br. s), 4.38 (2H, s), 4.25 (4H, m), 2.85 (3H, s). MS (ES) C19H15Cl2FN4O3 requires: 436/438, found: 437/439 (M+H)+.
