Nuclear magnetic resonance carboxylic acid-containing

Nuclear magnetic resonance studies revealed that normal prothrombin contains y-carboxyglutamate, a formerly unknown residue that evaded detection because its second carboxyl group is lost on acid hydrolysis during amino acid analysis. The abnormal prothrombin formed subsequent to the administration of anticoagulants lacks this modified amino acid. In fact, the first 10 glutamate residues in the amino-terminal region of prothrombin... 

Citreoviridin 1, C23H30O6CH3OH, was shown to contain one methoxy group and six double bonds. Permanganate oxidation of this compound in pyridine afiTorded a carboxylic acid (2), which contained one methyl, one methoxy, and one carboxy group. Infrared (ir) and ultraviolet (uv) absorption spectra of 2 indicated that this acid contained an a-pyrone moiety. The substitution on the pyrone ring was evident from the nuclear magnetic resonance (NMR) spectral data. 

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