The acid-catalyzed dehydration of 1-benzylamino-1-deoxy- d- threo-pentulose, 1-dibenzylamino-1-deoxy- d-fructuronic acid, and d-glucuronic acid

Abstract

Three compounds, 1-benzylamino-1-deoxy- d- threo-pentulose ( 1), 1-dibenzylamino-1-deoxy- d-fructuronic acid ( 2), and d-glucuronic acid ( 3) were converted into 2-furaldehyde in acidified, tritiated water. In the latter system, the 2-furaldehyde derived from 1 contained 13% of the activity of the solvent at the aldehyde carbon and 9% at positions 3–5 of the furan ring; that from 2 contained 8% at the aldehyde carbon and 29% at positions 3–5; and that from 3 contained 18% at positions 3–5 In deuterium oxide, the 2-furaldehyde derived from 1 contained 14 atom % of deuterium at position 3, 5% at position 4, and 0% at position 5. That from 2 contained 50% at position 3, 44% at position 4, and 7% at position 5. That from 3 contained 35% at position 3, 15% at position 4, and 5% at position 5. The data for 1 are discussed relative to prior data on incorporation collected for d-xylose Incorporation data for both 2 and 3 are qualitatively consistent with a decarboxylation step involving a β,γ-unsaturated, carboxylic acid intermediate. A mechanism for the decarboxylation of hexuronic acids is presented.