A Urea-Linked Glucosamine Dimer as a Building Block for the Synthesis of Linear and Cyclic Neosaccharides

A novel urea-linked glucosamine dimer was obtained through a modification of the standard oxazolidinone closure reaction on a 2,3-amino alcohol monomer and fully characterized by NMR spectroscopy and by molecular mechanics and dynamics techniques. A mechanism was proposed for the dimerization reaction that was based on the formation of a 2,3-bis[(p-nitrophenoxy)carbonyl] intermediate. Chemoselective manipulations on the orthogonal protecting group pattern of the dimer - especially on its unprecedented oxazolidinone-urea-oxazolidinone system -gave an alcohol building block that was useful for access to higher linear and cyclic neosaccharides. The conformational features and 3D-characterization of a novel carbamate-linked neodisaccharide macrocycle was accomplished through molecular mechanics and dynamics calculations.