Phosphoryl trichloride (1.m7 ml, 10.8 mmol) was added to a solution of (S)—N-(2-(4-chlorophenyl)-2-oxoethyl)-2-(1,3-dioxoisoindolin-2-yl)propanamide (2.162 g, 5.83 mmol) in toluene and heated at 110° C. for 15 hours. Dilute with dichloromethane (50 ml), wash with saturated sodium bicarbonate solution, water, brine, dried and concentrated in vacuo. Flash column chromatography (silica, 80 g) eluting with 0-50% EtOAc/DCM afforded the pure product 430 mg (yellow foam). HRMS(B) tR=1.42 min; MS m/z 353.1
