ISSN:
0749-1581
Keywords:
NMR
;
1H NMR
;
Enantiomer discrimination
;
Chiral solvating agents
;
Cyclic hemiacetals
;
Cyclic methyl acetals
;
Hydroxamic acids
;
Chemistry
;
Analytical Chemistry and Spectroscopy
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The discrimination of enantiomeric cyclic hemiacetals and methyl acetals derived from hydroxamic acids and lactams with the 2H-1,4-benzoxazin-3(4H)-one and 2H-1,4-benzothiazin-3(4H)-one skeleton was investigated using (S)-(-)-phenylethylamine, (-)-quinine, β-cyclodextrin and, for the first time, (5R,11R)-(+)-2,8-dimethyl-6H,12H-5,11- methanodibezo [b,f] [1,5]diazocine, a Troeger's base enantiomer, as chiral solvating agents (CSA). Conditions for the enantiomeric discrimination of six configurationally stable methyl acetals are reported. 2,4-Dihydroxy-2H-1,4-benzoxazin-3(4H)-one and its 7-methoxy derivative, bioactive aglucones from Gramineae species, are the first cyclic hemiacetals that could be differentiated into enantiomers by means of 1H NMR, despite their oxo-cyclo tautomerization that prevented enantioseparation by chromatography or capillary electrophoresis. However, 2-hydroxy-2H-1,4-benzothiazin-3(4H)-ones (thiohemiacetals) could not be differentiated by the use of these CSA. The influence of the structure of the enantiomers, CSA, temperature and concentration on the size of the chemical shift anisochrony is discussed.
Additional Material:
2 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/mrc.1260321205
Permalink
