Alloxazines

Alloxan forms an oxime (1007) which is the same compound, violuric acid, as that formed by nitrosation of barbituric acid likewise, a hydrazone and semicarbazone. Reduction of alloxan gives first alloxantin, usually formulated as (1008), and then dialuric acid (1004 R = OH) the steps are reversible on oxidation. Vigorous oxidation with nitric acid and alkaline hydrolysis both give imidazole derivatives (parabanic acid and alloxanic acid, respectively) and thence aliphatic products. Alloxan and o-phenylenediamine give the benzopteridine, alloxazine (1009) (61MI21300). 

Alloxazines (295) have been considered to exist as such, and not as isoalloxazines (296, R = H), because their ultraviolet spectra and... 

Flavins (152), benzoamielated derivatives of lumazine (145), are implicated in a variety of photobiological processes such as photodynamic action, phototropism, phototaxis, and photosynthesis. The biologically active H form 152a of alloxazine (R = R = R = = H) is less stable in... 

A special influence on the course of a reaction by a neighboring group is shown in the reactions of 5-acetyl-leuco(iso)alloxazines - with diazomethane. The methylation occurs neither in the pyrimidine nor in the pyrazine ring, but on the hydroxyl group of a newly formed oxazoline ring. For example,... 

The fused system, pyrimido[4,5-h]pyrazine (219), is more commonly known as pteridine, a ring system which is present in such biologically important molecules as alloxazine, riboflavin, leucopterin, xanthopterin, and the coenzyme, flavin-adenine dinucleotide. 

Alloxazine 38 is a weak, nonxanthine antagonist that is slightly selective for the A2BAR. 

Virus, R. M., Ticho, S., Pilditch, M. Radulovacki, M. (1990). A comparison of the effects of caffeine, 8-cyclopentyltheophylline, and alloxazine on sleep in rats. Possible roles of central nervous system adenosine receptors. Neuropsychopharmacology 3 (4), 243-9. 

In LB films not only the interaction of chromophores but also their orientation can be controlled at the molecular level. Molecular orientation of chromophores has been determined by several methods including polarized UV/vis or IR absorption, second harmonic generation (SHG), Electron Spin Resonance (ESR), or resonance Raman scattering. We have measured the incident angle and polarization angle dependencies of polarized UV/vis absorption to study the molecular orientation of alloxazine, porphyrin, and carbazolyl chromophores, or 4,4 -bipyridinium radical cations in LB films[3-12]. Usually in-plane components of transition dipoles of chromophores are... 

This model has been successfully applied to J aggregates of cyanine dyes in a brick stonework arrangement [47,48]. However, this model cannot explain the spectral shift of chromophores having transition moments in two or more directions as shown in Figure 8 for long-axis and short-axis transition dipoles of carbazolyl chromophores, nor it can predict the orientation of chromophores with respect to the substrate. In order to explain such spectral shifts and molecular orientation of alloxazine and carbazolyl chromophores as mentioned above, we proposed a three-dimensional extended dipole model which takes a three-dimensional... 

Carell has recently presented the study of a flavin amino acid chimera to model riboflavin in DNA photolyases [68]. This amino acid LI (Fig. 20) was synthesized in an enantiopure fashion by building the alloxazine ring onto the epsilon amine of lysine. This coenzyme chimera was applied to the problem of repairing DNA damage caused by UV irradiation. LI was incorporated into an 21-residue peptide, P-1, possessing the sequence of the DNA-binding domain of the helix-loop-helix transcription factor MyoD. 

In such vesicle systems, the electrons are transported through the membrane. Electron carriers such as quinones or alloxazines in the vesicle wall enhance remarkably the rate of photoinduced charge separation. The vesicle system shown in Fig. 6 contains the surfactant Zn-porphyrine complex (ZnC12TPyP) in the wall 23). 

C(8) to be parallel with the nitrogen orbitals, thus providing evidence for the planarity of flavin semiquinones 2. More recent X-ray crystallographic data on the Cl. MP flavodoxin provide confirmatory data on the planarity of the iso-alloxazine ring in its one-electron reduced form. 

C. Preparation of Quinoxalines from Alloxazines, Diazepines, and Quinone Diimides... 

Pteridines, Alloxazines, Flavins, Vitamin B2 and Related Compounds Vitamin Bj and Related Compounds , G. R. Ramage and T. S. Stevens, in The Chemistry of Carbon Compounds , ed. E. H. Rodd, Elsevier, Amsterdam, 1960, vol. 4C, pp. 1760-1798. 

DPL Intermediate acceptors (alloxazine or vitamine Kj), when inserted into the membrane, increase 4>. Two-step photoactivation of electron transfer. (ZnC12TPyP+) = 100 (AF) 63... 

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