Synthesis and structural studies of 1-amino-1-deoxy-α-L-xylo-hexulopyranose: L-Sorbosamine
Ketosamines are an important class of glycoconjugates widely employed in clinical diagnostics and implicated in development of diabetic complications, intestinal infections, or advanced cancer, as well as in food organoleptic and nutritional value. We report on the first preparation and structural characterization of 1-amino-1-deoxy-L-sorbose (L-sorbosamine, L-SorNH2). The monosaccharide was synthesized from L-sorbose following a classic phenylosazone protocol. In aqueous solution, L-SorNH2 assumes an anomeric equilibrium consisting of 89.3% α-pyranose, 3.7% β-pyranose, 3.8% α-furanose, 2.4% β-furanose, and 0.9% acyclic keto tautomer. The α-pyranose anomer in crystalline L-SorNH2 × HCl adopts the 2C5 chair conformation, with bond lengths and valence angles comparing well with related sorbopyranose structures. All hydroxyl oxygen atoms, the ammonium group and chloride ion are involved in an extensive hydrogen bonding network which is formed by infinite chains with fused antidromic R76(14), R54(10), and R43(8) cycles. The Hirshfeld surface analysis suggests a significant contribution of the non-polar intermolecular contacts to the crystal structure, as well.
