Pyrrolo quinoline

As dehydrogenases (DH) are widely distributed enzymes, a number of studies have been carried out with these biocatalysts. For example, Willner el al. [20] have used a PQQ-monolayer functionalized gold electrode for the catalytic oxidation of NADH in the presence of Ca2+. In this scheme, the pyrrolo-quinoline quinine co-factor, PQQ, was covalently linked, as before for the GOx system [15, 20, 21], to the Au electrode,... 

C. Anthony, M. Ghosh, and C.C. Blake, The structure and function of methanol dehydrogenase and related quinoproteins containing pyrrolo-quinoline quinone. Biochem. J. 304, 665-674 (1994). 

Full -polarization in diradicals can give rise to zwitterionic products. First examples were studied in detail by Carpenter and coworker who investigated solvent effects on rates and product distribution in Myers-Saito cyclizations.64 Polar solvents and substitution patterns that stabilize either positive or negative charges (or both) favor the zwitterionic products. For example, the presence of a dimethylamino group leads to stabilization of cations and isolation of pyrrolo-quinolines, rather than pyrido-indoles from eneyne-carbodiimides, as reported by Wang and coworkers (Scheme 14).65... 

PYRROLO-QUINOLINE QUINONE (PQQ) THE PROSTHETIC GROUP OF METHANOL DEHYDROGENASE... 

The light-induced control of the electroactivity of charged redox-active substrates allows the functionalized electrode to be used to control electrochemical transformations. A system composed of two oppositely charged diffusional redox probes—positively charged 2,5-bis[[2-(dimethylbutylammo-nio)ethyl]amino]-l,4-benzoquinone (14) and negatively charged pyrrolo-quinoline quinone (PQQ) (15)—was used to demonstrate this behavior... 

As an alternative strategy to escape the drawbacks of the initial leads, the quinoline ring was retained but constrained in a pyrrolo-quinoline ring system as in SKF 96356 (166). This ring system has also formed the basis of compounds described by the Korea Research Institute of Chemical Technology [AU-006 (167), AU-461 (168), and DBM-819 (169)]. DBM-819 displays potency comparable to that of omeprazole in models of gastric acid secretion and ulceration (169). 

Methoxantin coenzyme (PQQ, pyrrolo quinoline quinone, 2,7,9-tricarboxy-lff-pyrrolo-[2,3- /]-quinoline-4,5-dione, 4,5-dihydro-4,5-dioxo-lfl-pyrrolo[2,3 quinoline-2,7,9-tri-carboxylic acid) [72909-34-3] M... 

Quinone containing redox enzymes are a much less widely studied group, and to date fewer examples have been characterized. The prosthetic group in this case is a quinone, pyrrolo-quinoline quinone (PQQ), and again it is a two-electron... 

The electrochemistry of the PQQ (pyrrolo-quinoline quinone) prosthetic group has been investigated at poly(pyrrole)-coated electrodes, and PQQ has been entrapped within poly(pyrrole) films " good electrochemistry was observed in both cases. Poly(pyrrole) has also been used to entrap adenosine triphosphate (ATP) anions, again by growing the film in the presence of the anion, " and as an electrode material for oxidizing ascorbate. " In the latter case the oxidation... 

Interesting constructs of molecules such as pyrrolo-pyridines, pyrrolo-quinolines, pyrrolo-pyrazines, pyrrolo-quinoxalines and pyrrolo-pyrimidines could be constructed by intramolecular Chichibain-type reaction. Davis and co-workers were the first to show the first of these examples, where p-methylazines react with nitriles to give the corresponding fused bicycle in the presence of excess base (2.5 equiv). For example, P-picoline reacts with benzonitrile in the presence of LDA to give the pyrrolo-pyridine adduct 61 in a 90% yield and traces of 62a. Under similar conditions and if... 

Pyrrolo quinoline quinone, PQQ 2,7,9-tricar-boxy-li/-pyrrolo [2,3-/ quinoline-4,5-dione, the cofactor of methanol dehydrogenase (EC 1.1.99.8) from Hyphomicrobium X and Melhylophilus methy-lotrophus, and of glucose dehydrogenase (EC 1.1.99.17) from Acinebacter cakoaceticus. [J. A. Duine et al. Eur. J.Biochem. 108 (1980) 187-192]... 

Besides the permselective properties, the electrocatalytic properties of ECP films can be also used for the amperometric detection of some target molecules. Accordingly, electrodes modified with PPy, polythiophene (PTh), PAni, and their derivatives were found to catalyze the electrochemical oxidation of ascorbic acid [127-129], NADH [115, 116,130], dopamine [128], pyrrolo-quinoline quinone [131] as a coenzyme of some oxidoreductases, and quinone and derivatives [132, 133]. Selectivity exhibited by these materials could be enhanced by the introduction of an appropriate substituent onto the polymer backbone. So, a facilitated electron transfer between cytochrome c and carboxylic acid or carboxylate-substituted PPy [134] or polyindole [135] has been observed. As such an effect was not obtained with unsubstituted polymer films, the cytochrome c-polymer interaction was e lained on the basis of binding between the polymer substituents and the lysine residues on the redox protein. 

---