Anhydro sugars VOLUME

On this subject Levene deals adequately with earlier work, much of which was due to his own efforts. Attention has chiefly been focused on the attainment of more refined methods for the characterization and estimation of amino sugars and laterly toward the elucidation of their structure. The whole problem of configurational relationships in the group is closely bound up with the study of anhydro sugars (see S. Peat, this volume, page 37) since such products are produced on deamination of amino sugars, a process which also leads to the added complication of Walden inversion. It is not surprising therefore that the direct mode of attack has not led very far. 

In this volume of Advances, Cerny and Stanek, Jr. (Prague) contribute a comprehensive article on the 1,6-anhydro derivatives of aldohexoses. This class of anhydro sugars, earlier termed the hexosans, constitutes by far the largest class of sugar anhydrides to have been studied. The scope of the topic is now so extensive that the Editors, in view of their earlier practice of limiting chapter size in individual volumes of Advances in the interest of diversification of subject material, were inclined to divide this chapter into two parts, to appear in successive volumes. However, as the latter practice has elicited some unfavorable reaction from readers on previous occasions, it was decided to present the article here in its entirety. The chapter complements previous ones on other classes of anhydro derivatives, in particular, recent ones on anhydrides of the oxirane (epoxide) and 2,5-anhydro (oxolane) types. 

Goodman has reviewed neighboring-group participation in Volume 22 of this Series,366 and this subject will therefore not be discussed comprehensively in the present article. However, Goodman specifically excluded from his review the formation of anhydro sugars by oxide ion displacements, and also the formation of anhydronucleosides ( cyclonucleosides ). These topics will therefore be discussed, together with ring contractions and alkoxyl participations, because most of the literature on these subjects has not been reviewed previously. 

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