Is the optical rotation sign/absolute configuration relationship still a problem? Examples taken from unnatural quaternary aminoacids
Résumé
The optical rotation sign/absolute configuration relationships of several alpha-methyl-alpha-arylglycines have been reinvestigated by crystallographic methods, as they have been found to be inconsistent in recent literature. Assignments previously made by enzymatic resolution, by analogy with natural tertiary aminoacids were found to be erroneous in the case of these quaternary aminoacids.