In a reaction flask 5-Benzyloxy-2-(4-benzyloxy-phenyl)-1H-indole No. 141 (5.90 g, 14.6 mmol) was mixed with CH2Cl2 (90 mL) was cooled down to 0° C. (the starting material did not completely dissolve in CH2Cl2). While stirring vigorously, a solution of chlorosulfonyl isocyanate (2.26 g, 16.0 mmol) in CH2Cl2 (25 mL) was added dropwise over a period of 45 min. The reaction was run at 0° C. for 2 hrs while detected by TLC for the formation of the insoluble N-chlorosulfonylamide intermediate. After this period, Et3N (1.47 g, 14.6 mL) in CH2Cl2 (25 mL) was added dropwise over 45 min at 0° C. The insoluble residue became soluble in the reaction solvent as the Et3N addition was approaching completion. The reaction was let go for the additional 1 hr at 0° C. and 2 hrs at rt. The progress of the reaction could be observed by the insoluble solid formation of the product as the reaction time went on. The solvent was stripped down and the solid residue purified by trituration with methanol to yield (4.0 g, 63.8%). Mp=238-242° C.; 1H NMR (DMSO) 12.31 (s, 1H), 7.88 (d, 2H, J=8.8 Hz), 7.48 (d, 4H, J=7.25 Hz), 7.55-7.30 (m, 7H), 7.23 (d, 2H, J=8.8 Hz), 7.14 (d, 1H, J=2.4 Hz), 6.97 (dd, 1H, J=2.2 Hz, 8.8 Hz), 5.20 (s, 2H), 5.17 (s, 2H); MS eI m/z 430 (M+).
