## Abstract Schiff base formation by condensation of pyridoxal phosphate or pyridoxal with octopamine in aqueous or methanolic medium was investigated by ^13^C NMR. Enolimine forms are favoured in methanolic solution, whereas in aqueous solution the predominant ketoenamine forms show a hydrogen bon
A 13C NMR study of pyridoxal-5′-phosphate oxime
✍ Scribed by Timo Korpela; Juhani Lundell; Eila Mäkinen
- Publisher
- John Wiley and Sons
- Year
- 1979
- Tongue
- English
- Weight
- 287 KB
- Volume
- 12
- Category
- Article
- ISSN
- 0749-1581
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✦ Synopsis
Abstract
Pyridoxal‐5′‐phosphate amino‐oxy acetate oxime was titrated in water, over the pH range 4–12, and the changes followed using ^13^C NMR. The results were compared to those of analogous Schiff's bases presented in the literature. The chemical shifts and titration curves of the oxime were appreciably different from those of the Schiff's bases, and the differences are explained as being due to the absence of ketoenamine‐enolimine tautomerism in the oxime. The low chemical shift value and the large changes of the oxime azomethine carbon during titration, as compared to the Schiff's bases, are discussed. The high stability of the oximes in water makes them suitable as model compounds for some tautomeric forms of the Iess stable Schiff's bases.
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## Abstract The composition of the mixture from the reaction of the basic amino acids ornithine or lysine with pyridoxal‐5′‐phosphate was investigated in D~2~O by ^1^H NMR and was found to be dependent on pH, α attack being favoured at acid pH and ω attack in basic solutions.
## Abstract ^1^H and ^19^F NMR spectra were obtained for six Schiff bases (aldimines) formed by pyridoxal‐5′‐phosphate (PLP) with four fluorinated or their two parent non‐fluorinated α‐amino acids (phenylalanine and α‐aminobutyric acid). p__K__~A~ Values were derived from ^1^H and ^19^F titration c
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Carbon-13 NMR data of [iilmetacyclophane (la), its 8,ll-dihalosubstituted derivatives lb-ld and of some model compounds are reported and discussed. A remarkable downfield shift is observed for the aromatic carbon between the bridging carbons; this is tentatively ascribed to long-range effects of the
The "C and 'H NMR spectra of six N-5'-methylsalicylideneanilines have been studied. Correlations of the chemical shifts of C-a (azomethine carbon) and C-4' with the cr, F, R , crI and a: parameters have been examined for N-5'-methylsalicylideneanilines, and also for N-benzylideneanilines and N-salic