To a cold (0° C.) solution of the hydrochloride salt of Intermediate 1 (7.1 g, 30 mmol), (Z)-2-(2,2-dimethyl-5-oxo-1,3-dioxolan-4-ylidene)acetic acid (5.6 g, 33 mmol), EDC (6.8 g, 36 mmol), and HOBt (5.4 g, 36 mmol) in DMF (200 mL) was added N-methylmorpholine (13 mL, 120 mmol). The reaction mixture was allowed to warm to rt, stirred for 16 h, diluted with EtOAc (500 mL), the solution washed with saturated aqueous NaCl:water (1:1), and the organic portion dried over MgSO4, filtered and evaporated to dryness in vacuo. The product was purified by silica gel chromatography (330 g silica gel) to obtain 9.68 g (89%) of Intermediate 5. HPLC/MS (Method C) RT=3.40 min; [M+H]+ 359; 1H NMR (500 MHz, chloroform-d) (δ ppm): 1.76 (s, 6H), 1.88 (quin, J=7.42 Hz, 2H), 2.64 (t, 2H), 3.37 (q, 2H), 5.86 (s, 1H), 6.37 (br. s., 1H), 7.01-7.07 (m, 1H), 7.28 (d, 1H), 7.35 (d, J=7.70 Hz, 1H).
