Selective C‑2 Alkylation of Tryptophan by a Pd(II)/Norbornene-Promoted C–H Activation Reaction

A palladium­(II)-catalyzed norbornene-mediated regioselective alkylation at the C-2 indole position of <i>N</i>-<i>tert</i>-butyloxycarbonyl (Boc)-protected (<i>S</i>)-tryptophan ethyl ester is reported. The protocol employs mild reaction conditions and is tolerant of a range of functional groups. The reaction proceeds without racemization at the stereogenic center of the amino acid.