Synthesis of Divalent Carbohydrate Mimetics by Reductive Amination with Enantiopure 1,2-Oxazines as Precursors
J. Salta, H.-U. Reissig
A direct approach to mono- and divalent carbohydrate mimetics starting from an enantiopure 1,2-oxazine derivative is described. After the Lewis acid induced rearrangement and subsequent reduction to provide the expected bicyclic 1,2-oxazine derivative as major component, a new tricyclic compound resulting from a different rearrangement pathway was isolated in small amounts. A smooth and optimized method for the hydrogenation of the bicyclic 1,2-oxazine derivative is presented, affording the desired aminopyran with d-idopyranose configuration. By reductive amination this aminopyran was connected with different aldehydes to furnish N-alkylated compounds. Reductive amination using 1,5-pentanedial resulted in the formation of a piperidine ring. With rigid aromatic dialdehydes the desired divalent compounds were obtained in good to excellent yields. Similar divalent carbohydrate mimetics were prepared from serinol.