Overall ring conformation

Anthracenes are planar by virtue of the necessity of maintaining aromaticity. When the central ring is reduced, an overall "butterfly" conformation is achieved. For reasons that are not yet understood at the molecular level, this conformation is often associated with central antidepressant activity. 

More than any other factors, single-bond conformation and ring conformation dictate overall molecular size and shape. Thus, proper assignment of ground-state conformation is a very important task for calculation. 

This method can be extended (62) to complexes of amino alcohols, such as L-(+)-alaninol, which has a similar skeletal structure to (+)-propylenediamine. However, it is not applicable to amino acid chelate rings as these are nearly planar, and ring conformational effects contribute little to the overall stability of the complex. 

Relatively small differences in the puckering of the ribofuranose ring are amplified in the orientation of the 0(30 and 0(5 ) atoms to which, in the nucleic acids, the phosphate groups are bound. For this reason, extensive analyses have been made of the relationship between ring conformation and the overall stereochemistry of the nucleic acid molecules. 

It has been shown that stereoelectronic effects play an important role in many enzyme-catalyzed biochemical reactions, as, for example, in ribozymes [2-4], serine proteases [5], lysozymes [6], and ribonucleases [3, 7], While most of the studies on stereoelectronic effects were conducted on pyranoid forms of sugars, the relationship between stereoelectronic effects and furanoid ring conformations, to the best of our knowledge, is almost totally neglected. This is a big void since the conformations of furanoid forms of sugars are of great importance for overall conformations of ribo- and deoxyribonucleic acids (RNA and DNA). 

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