This invention is concerned with improved processes for reductive alkylation of glycopeptide antibiotics. The improvement residing in providing a source of copper which results in the initial production of a copper complex of the glycopeptide antibiotic. Reductive alkylation of this complex favors regioselective alkylation and increased yields. Copper complexes of the glycopeptide antibiotic starting materials and of the alkylated products are also part of the invention.