A solution of DIAD (1.80 g, 8.89 mmol) in dioxane (5 mL) was added to a solution of triphenylphosphine (2.33 g, 8.89 mmol) in dioxane (20 mL) at 0° C. under a nitrogen atmosphere. After 10 min stirring, 1-[3-phenyl-1-(toluene-4-sulfonyl)-1H-indol-2-yl]ethanol (1.74 g, 4.44 mmol) in dioxane (15 mL) was added followed by diphenylphosphoryl azide (1.47 g, 5.53 mmol) in dioxane (5 mL). The reaction mixture was stirred at 20° C. for 16 h then the reaction mixture was diluted with DCM and purified by column chromatography (Si—PCC, gradient 10-100% DCM in pentane) affording the title compound as a gum (1.39 g, 75%). LCMS (Method C): RT 4.77 min [M-N3]+ 374.1.
