M. Crisma, G. Valle, F. Formaggio
May 7, 1997
Citations
0
Influential Citations
14
Citations
Journal
Journal of the American Chemical Society
Abstract
The structures of the 2-alkoxy-5(4H)-oxazolones derived from 2,2,6,6-tetramethyl-4-[(benzyloxycarbonyl)amino]-1-oxypiperidine-4-carboxylic acid and 2,2,6,6-tetramethyl-4-[(9‘-fluorenylmethoxycarbonyl)amino]-1-oxypiperidine-4-carboxylic acid have been solved by single-crystal X-ray diffraction. The overall geometry of their oxazolone ring compares well with that of 2-alkyl-5(4H)-oxazolones. However, the bond distance from C2 to the exocyclic O(2) atom is shorter than expected for a (sp2)C−O single bond, thus suggesting a significant involvement of a O(2) lone pair in the electron delocalization of the CN π-system. These two structures represent the first examples of 2-alkoxy-5(4H)-oxazolones in the crystal state. Ab initio molecular orbital calculations have been performed on (4S)-2-methoxy-4-methyl-5(4H)-oxazolone and (4S)-2,4-dimethyl-5(4H)-oxazolone [as simple models for 2-alkoxy- and 2-alkyl-5(4H)-oxazolones, respectively, derived from the chiral protein amino acid l-Ala] both in the neutral and deprot...