Ag-Catalyzed diastereo- and enantioselective synthesis of beta-substituted tryptophans from sulfonylindoles.

The asymmetric catalytic synthesis of beta-substituted tryptophan derivatives was realized in high diastereo- and enantioselectivity by the reaction of glycine derivatives with sulfonylindoles in the presence of catalyst derived from AgCl and a commercially available chiral monodentate phosphoramidite ligand. The resulting adduct was readily converted to beta-substituted tryptophan in 95% overall yield for two steps, which presented a highly efficient route to chiral beta-substituted tryptophan.