Stir a stir solution of 4-(3-cyclopentyl-indole-1-sulfonyl)-benzoic acid (19.0 g, 51.43 mmol) in anhydrous THF (250 mL) cool to 5° C. under N2 add N-methylmorpholine (5.8 mL, 52.72 mmol) and 2-chloro-4,6-dimethoxy-1,3,5-triazine (CDMT) (9.0 g, 51.34 mmol). Stir the mixture for 1 h and add a solution of 4-aminomethyltetrahydropyran (6.6 g, 57.34 mmol) in dry THF (75 mL) by dropping funnel. Warm the mixture to room temperature and stir for 3 h. Cool the mixture to 5° C., add 1N HCl (250 mL) and partition the resulting solution with ethyl acetate (250 mL). Extract the organic layer with aqueous saturated sodium bicarbonate (250 mL), brine (250 mL), and dry over sodium sulfate. Concentrate to give a foam, dissolve in minimum methylene chloride and add to a flash 65 M cartridge. Elute with 3:2 hexanes/ethyl acetate to give the major product as a solid, filter from hexanes, and dry (20 mm Hg, 40° C.) to give the homogeneous white solid (20.5 g, 85%); MS (ESI) m/z 467 (m+H).
