Conformational analysis, septanose

The conformational analysis of monosaccharides, disaccharides, and ohgosaccharides is reviewed. Conformational terms are introduced through examination of the conformations of cyclohexane and cyclopentane then applied to the pyranose, furanose, and septanose rings. Concepts such as the anomeric effect are discussed. Topics of current interest, such as hydroxymethyl group and hydroxyl group rotation and disaccharide conformations are summarized. Physical methods for studying conformation are outlined. 

Even though the yields of the septanose derivatives in these reactions are decidedly modest, the products were isolated in sufficient quantities to permit analysis of their structures and conformations. Importantly, these routes provided enough of the respective septanoses to allow the preparation of alkylated and acylated glycoseptanosyl isomers. 

While the pyranose and furanose ring forms of the sugars dominate the carbohydrate literature, the uncommon septanose ring forms have long intrigued sugar chemists, with particularly notable contributions by Stevens in Australia. The chapter in this volume from Saha and Peczuh (Storrs, Connecticut) provides a comprehensive overview of the subject from both the synthetic and structural viewpoints and presents a detailed analysis of the conformational behavior of these ring forms. It may be noted... 

The purpose of this chapter is to focus on ring expansion methodologies to the preparation of these structures, in addition to analyzing their conformational features as revealed by recent reports. It is also important from an overall point of view of progress in this field that septanose formation through cyclization of linear precursors is also presented before discussion on ring expansion methodologies and subsequent structural analysis. 

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