Lactone Formation from Mono- and Dicar- Boxylic Sugar Acids

The most recent phase of the work on simple carbohydrates is concerned with isomerisms occasioned by differences in size of the oxidic ring. The first observations which brought to light the existence of such isomers were made by Nef’ and by E. Fischer.2 Nef discovered two isomeric galactonic lactones and Fischer a third isomer of l-methyl glucose. Isomers of this type have been discovered for the derivatives of many monosaccharides through the efforts of Irvine3 and of other workers of his school, through those of Hudson” and others. Very recently isomers of this t.ype have been described for lactones of methylated galactonic acid (Pryde and coworkersj and Haworth and coworkers ) and of methylated mannonic acid (Levene and Meyer’). Fischer and Irvine have noted that the new isomeric l-methyl hexoses were less “stable” than the common forms and that carbon atom (1) in the new forms is more reactive than the corresponding atom in the common forms. From the observations of Haworth, Ruell, and Westgarth it follows that tetramethyl galactonic1, 4-lactone is more “stable” than its 1,8isomer. One of the two tetramethyl mannonic lactones prepared by Levene and Meyer