To a white suspension of 19 (0.075 g, 0.271 mmol) and NEt3 (0.292 mL, 2.71 mmol) in anhydrous CH2Cl2 (2 mL) at 0° C. under an inert atmosphere was added to a colourless solution of N,N-dimethylsulfamoyl chloride (0.408 mL, 3.80 mmol) in anhydrous CHACl2 (3 mL). The resulting white suspension was left to stir under an inert atmosphere at room temperature for 70 h forming a clear orange/brown solution. The reaction mixture was diluted in CH2Cl2 (30 mL) and washed with distilled H2O (30 mL×3) and brine (30 mL). The organic fraction was separated, dried (MgSO4), filtered and solvent removed in vacuo to leave yellow residues. Column chromatography (CH2Cl2/acetone 75:25) eluted 21 as a viscous yellow oil (0.093 g, 90%); 1H NMR δH (270 MHz, CDCl3) 3.00 (s, 6H), 5.44 (s, 2H), 7.28-7.33 (m, 2H), 7.39 (d, J=8.7 Hz, 2H), 7.53 (d, J=8.7 Hz, 2H), 7.76 (d, J=7.9 Hz, 1H), 8.00 (s, 1H) and 8.18 (s, 1H); LCMS (APCI−) m/z (rel intensity) 382 (100, [M−H]+; HRMS (ES+) m/z calcd. for C18H18N5O3S [M+H]+: 384.1125, found 384.1143.
