OPTICAL ROTATORY DISPERSION OF SUGARS .4. CONFIGURATION AND CONFORMATION OF URONIC ACIDS AND ACETAMIDO SUGARS

The optical rotatory dispersion properties of uronic acids and acetamido sugars have been investigated. For both categories of sugars, two optically active transitions have been implicated as the foremost factors determining the shapes of the rotatory of dispersion curves in the spectral region below 230 nm. By a study of difference curves, the rotatory properties associated with the individual amide and carboxyl chromophores were isolated. The curves for the uronic acids were characterized by positive Cotton-effect peaks near 220 nm and negative Cotton effects shown below 190 nm. These features were ascribed to the influence of the equatorial carboxyl group on the pyranoid ring. The acetamido sugars were found to exhibit curves having a Cotton-effect minimum near 220 nm and a Cotton-effect peak at 200 nm. The present data have also been related to the results obtained previously for sugars lacking acetamido or carboxyl substituents, and these conform with the established views relating far-ultraviolet rotations to the configuration and conformation of the cyclic forms of sugars. © 1968.