Phenol Oxidation Reactions

Abstract

Dedicated to Professor Dr. Hans Brockmann on the occasion of his 60th birthdayThe use of well-known phenol oxidation reactions for the preparation of compounds arising from C-C and C-0 coupling has recently received increased attention. A selection from the large number of products obtainable by oxidation of mono-and polyhydric phenols and a discussion of the reaction mechanisms indicate the scope of this method. The formation of hydroxyphenylquinones and orceine dyes from resorcinol derivatives is explained. The synthesis of natural products by way of phenol oxidations is briejiy discussed.

Tyrosyl radical generated by myeloperoxidase catalyzes the oxidative cross-linking of proteins.

“…It also remains to be determined if other amino acids are oxidized by myeloperoxidase. Because L-tyrosine is the most easily oxidized aromatic amino acid (26), and phenols are known to be unusually susceptible to one electron transfer reactions (8)(9)(10), L-tyro- (24), L-tyrosine (9-11), vitamin E (24), and ascorbate (24). The repair reaction may explain both the stimulation of neutrophil-dependent dityrosine cross-linking by superoxide dismutase and the inhibition of myeloperoxidase-catalyzed BSA cross-linking by high concentrations of L-tyrosine.…”

“…In contrast to hydroxyl radical, (HO), the tyrosyl radical is relatively stable and selectively reactive (9,10,27,28). Dityrosine may be a significant product oftyrosyl radical in biological systems, making the compound a potentially useful marker for oxidation.…”

“…Studies with phenols and L-tyrosine oxidized by ferricyanide (9-1 1 ) indicate that the enzymatic reaction is likely to involve phenoxyl radical generation (6,12). Radical coupling of phenoxyl radical yields orthoortho, ortho-para and para-para dimers, reflecting the distribution of free-electron density on the aromatic ring (9)(10)(11). Because the para position is blocked by a bulky substituent in tyrosyl radical, the major product of the reaction is o,o'-dityrosine (6,9,10,12):…”

Reactions of 1-Naphthols with .PI.-Acceptor p-Benzoquinones: Oxidative Aryl Coupling vs. Non-Oxidative Electrophilic Arylation

“…4) The usual methods for construction of bi-and triaryl frameworks can be divided into the following categories: (i) oxidative biaryl coupling (so-called phenolic oxidation) of various arenas including metal phenolates 5) using a chemical method 6) or an electrochemical, 7) (ii) biaryl coupling between aryl halides and arylmetal compounds 8) or arylmetal species, 9) and (iii) electrophilic arylation of quinone derivatives with hydroxyarenes in the presence of acids or bases. [10][11][12][13][14][15] Nature makes extensive use of the oxidative coupling reaction for the selective construction of complex compounds from simple starting materials, such as naphthols and phenols. We have focused on the oxidative coupling (or dimerization) of 1-naphthols (NPOHs) in order to develop a method for constructing biaryl substructures, aiming at biomimetic synthesis of natural products such as 2,2Ј-binaphthols, 2,2Ј-binapthylquinones and their derivatives.…”

Estudos conformacionais de seqüências hidrofóbicas de domínios de receptores acoplados a proteínas G (GPCR) e da proteína G. Um estudo de CD e espectroscopia de fluorescência

“…Na literatura (226\ bandas como aqui observadas são também características de bitirosina. Geralmente esse dímero covalente se forma a partir de condições oxidantes (227), porém sua formação por ação de luz também foi descrita (228).…”