DMSO (5 eq.) was dissolved in DCM and the solution was cooled to −78° C. To the stirred solution oxalylchloride (2.5 eq.) was added and the mixture was left stirring for 30 min. A solution of methyl 1-allyl-3-cyclohexyl-2-[2-(hydroxymethyl)-4-methoxyphenyl]-1H-indole-6-carboxylate (1 eq.) in DCM (0.25M solution) was added and the mixture was left stirring for 30 min at −78° C. Et3N (8 eq.) was added and the mixture was allowed to warm to 0° C. At this temperature stirring was continued for 2 h, and then stirring was continued at RT overnight. The mixture was diluted with DCM, and then washed with water, 1N HCl, saturated aq. NaHCO3 solution and with brine. After drying over Na2SO4 all volatiles were evaporated in vacuo. The residual material was purified by flash chromatography (PE:EtOAc, 9:1). After evaporation of the solvents the product was obtained as a yellow foam (88%). MS (ES+): 432.1 (M+H+).
