Regioselective acylation at the 5- or 6-position of l-tryptophan derivatives

The reaction of 1-acyl tryptophan derivatives with chloroacetyl chloride or the reaction of 1-tosyl tryptophan derivatives with acetyl chloride provides the corresponding 6-acylation products, while acylation of the 3-oxo tryptophan derivative gives a 5-substituted product.