Oxalyl chloride (2.5 eq., 2M solution in DCM) was added at −70° C. under nitrogen atmosphere to a solution of DMSO (5 eq.) in anhydrous DCM and the mixture was stirred for 30 min; a solution of methyl 1-allyl-3-cyclohexyl-2-[2-(hydroxymethyl)phenyl]-1H-indole-6-carboxylate in DCM was then added and stirring was continued at the same temperature for 30 min. before NEt3 (8 eq.) was added. After stirring for 20 min. at 0° C. the mixture was diluted with DCM, then washed with water, 1N HCl, saturated aq. NaHCO3 solution and brine. The organic phase was dried over Na2SO4 and evaporated in vacuo. The residual material was used in the next step without purification. MS (ES+): 402.2 (M+H+).
