Base catalysed isomerisation of aldoses of the arabino and lyxo series in the presence of aluminate Original Research Article

Base-catalysed isomerisation of aldoses of the arabino and lyxo series in aluminate solution has been investigated. l-Arabinose and d-galactose give l-erythro-2-pentulose (l-ribulose) and d-lyxo-2-hexulose (d-tagatose), respectively, in good yields, whereas lower reactivity is observed for 6-deoxy-d-galactose (d-fucose). From d-lyxose, d-mannose and 6-deoxy-l-mannose (l-rhamnose) are obtained mixtures of ketoses and C-2 epimeric aldoses. Small amounts of the 3-epimers of the ketoses were also formed. 6-Deoxy-l-arabino-2-hexulose (6-deoxy-l-fructose) and 6-deoxy-l-glucose (l-quinovose) were formed in low yields from 6-deoxy-l-mannose and isolated as their O-isopropylidene derivatives. Explanations of the differences in reactivity and course of the reaction have been suggested on the basis of steric effects.