Scalable Synthesis of Anomerically Pure Orthogonal-Protected GlcN₃ and GalN₃ from d‑Glucosamine

An improved and scalable synthesis of orthogonally protected d-glucosamine and d-galactosamine building blocks from inexpensive d-glucosamine has been developed. The key reaction is an inversion/migration step providing access to a fully orthogonal protecting group pattern, which is required for microbial oligosaccharide synthesis. The method can be carried out on a multigram scale as several of the reactions can be purified by crystallization to give anomerically pure products.