The Lobry De Bruyn-Alberda Van Ekenstein Transformation

This chapter discusses the Lobry de Bruyn-Alberda van Ekenstein transformation. The Lobry de Bruyn-Alberda van Ekenstein transformation has usually been considered to embrace both epimerization of aldoses and ketoses and aldose-ketose isomerization. Actually, Lobry de Bruyn and Alberda van Ekenstein observed all three reactions, so that an experimental basis for defining the transformation has existed from almost the time of its first recognition. The experimental limits of the transformation have never been extended beyond those established in the original investigations. The history of the mechanism of the Lobry de Bruyn-Alberda van Ekenstein transformation begins with the first description of its reactions. Thus, Lobry de Bruyn and Alberda van Ekenstein proposed that the transformation might take place by intramolecular transfer of hydrogen in hemiacetal intermediates, which they considered were formed from the aldoses by addition and removal of water. Soon after this, Wohl and Neuberg suggested the enediol intermediate for aldose-ketose isomerization. The enolization mechanism apparently won nearly immediate acceptance and it has since dominated the field. The first 30 years of the transformation seem to have been marked more by speculations on the mechanism than by experiments designed to elucidate it.