1,1-Dioxo-3-butyl-3-ethyl-5-phenyl-8-hydroxy-2,3,4,5-tetrahydro-1,5-benzothiazepin (WO9616051; 0.40 g, 1.07 mmol), ethyl bromoacetate (0.23 g, 1.38 mmol), sodium carbonate (0.50 g, 4.7 mmol) and tetrabutylammonium bromide (30 mg, 0.093 mmol) were added to MeCN (10 ml). The mixture was refluxed for 18 hours and then evaporated under reduced pressure. The residue was extracted with DCM/water. The DCM layer was separated and evaporated under reduced pressure. The residue was purified by column chromatography. The product was eluted with DCM/EtOAc (90:10). 0.480 g (97%) of the title compound was obtained. NMR (300 MHz) 0.7–0.85 (m, 6H), 1.0–1.7 (m, 11H), 3.1–3.3 (m, 2H), 3.6–3.8 (m, 2H), 4.3 (q, 2H), 4.6 (s, 2H), 6.9–7.3 (m, 7H), 7.5 (d, 1H).
