Isomerisation of aldoses in pyridine in the presence of aluminium oxide Original Research Article

Addition of aluminium oxide to boiling pyridine solutions of d-xylose, l-arabinose, d-mannose and d-glucose strongly increased the reaction rate of the aldose–ketose transformation. The maximum content of 2-ketose was reached after less than 2 h for the aldopentoses and 3 h for the aldohexoses. d-threo-2-Pentulose (xylulose) was prepared from d-xylose, and isolated as its O-isopropylidene derivative, the yield was nearly twice that compared to that usually obtained in the classical Lobry de Bruyn–Alberda van Ekenstein transformation in pyridine.