Synthesis of a Derivative of 1-Deoxy-2,3-D-Threo-(and D-Erythro) Hexodiulose, an Intermediate in the Acid and Base Catalyzed Degradation of Hexoses

Abstract

1-Deoxy-2,3-hexodiuloses are thought to be key intermediates in the conversion of hexoses to saccharinic acids (in alkaline systems), as well as to furans and related derivatives in acidic systems. The 5,6-O-isopropylidene derivative of the title compound was prepared by condensing 2,3-O-isopropylidene-B-glyceraldehyde with propyne via a Grignard reaction, followed by oxidation of the -O-acetyla-ted epimers to the diketones using a ruthenium catalyst and iodosylbenzene as the oxidant. Yields were in excess of 90% for each step, and no evidence of cleavage of the triple bond to the carboxylic acid was observed. Qualitative tests showed that the -O-isopropylidene-diulose is very unstable to both acids and bases, but that it is moderately stable at elevated temperatures (80 [ddot]C) and toward oxygen in aqueous dioxane solutions.