A flask is charged with 2-(1-benzyl-3-hydroxy-2-oxo-2,3-dihydro-1H-indol-3-yl)-N,N-dimethyl-acetamide (Example 18) (10 g, 30.83 mmol), N-chloro succinimide (NCS) (4.12 g, 30.83 mmol), acetic acid (40 mL), and toluene (20 mL). The orange suspension is then stirred over night and becomes a homogeneous solution. After the addition of about 5 mL of water, the solvent is removed on the rotavapor. To the residue, water is added, and the product is extracted with chloroform. After drying and removal of solvent 11 g of crude product is obtained which after chromatography on silica (toluene:ethyl acetate 1:1) gives the title product (9.76 g, 88%) as yellow foam. 1H-NMR (CDCl3,300 MHz) δ 2.74, 3.08 (AB, 2H, 2J=16.3 Hz, CH2CONMe2); 4.85 (s, 2H, NCH2Ph); 6.32 (br s, 1H, OH); 6.58 (d, 1H, 3J=8.2 Hz, H-7); 7.10 (dd, 1H, 4J=2.0 Hz, H-6); 7.13-7.32 (m, 5H, Ph); 7.46 (d, 1H, H-4). 13C-NMR (CDCl3, 75 MHz) δ 35.77, 37.77 (N(CH3)2); 38.80 (CH2CONMe2); 44.27 (CH2Ph); 74.65 (C-3); 110.72 (C-7); 125.10 (C-4); 127.33 (Ph ortho-C); 127.90 (Ph para-C); 128.54 (C-5); 129.00 (Ph meta-C); 129.49 (C-6); 132.80 (C-9); 135.26 (C-15); 141.08 (C-8); 170.31 (C-11); 175.96 (C-2).
