Selective Formation of Chromogen I from N‑Acetyl‑d‑glucosamine upon Lanthanide Coordination

We report two nonanuclear lanthanide complexes, [Ln94-O)­(μ3-OH)8(LH)4(OAc)4(H2O)12]·5ClO4·24H2O (Ln = Gd, 1; Dy, 2), where LH2– is the doubly deprotonated chiral ligand Chromogen I (2-acetamido-2,3-dideoxy-D-erythro-hex-2-enofuranose), one of the many products from the dehydration of N-acetyl-D-glucosamine (GlcNAc). Mass spectroscopic studies established the solution stability of these clusters. Through hydrogen bonding, the cluster complex self-organizes into a nanostructured 54-metal cagelike assembly featuring six of its units occupying the vertices of an octahedron. Free Chromogen I can be obtained in pure form and high yield by a straightforward workup of the cluster complex. This is the first report of dehydrating GlcNAc without the need of a catalyst or forcing conditions.