Hydroxy methoxy

Methoxypyrazines (31) have been prepared by diazomethane methylation of 2-hydroxy-3-isobutylpyrazine (60, 311, 367), 2-hydroxy-3-isopropylpyrazine (59, 367), 2-hydroxy-3-propyl(ethyl or hexyl)pyrazine (367), 3-hydroxy-2-isobutyl-5(and 6)methylpyrazine and 2-hydroxy-3-isobutyl-5,6-dimethylpyrazine (368), 2,3-dihydroxypyrazine (832), 2-hydroxy-5-methoxy- and 2,5-dihydroxy-3,6-diphenyl-pyrazine (832), 2-hydroxy-6-methoxy(and benzyloxy)pyrazine (832), 2,6-dihydroxy-3,5-diphenylpyrazine (873), 2,3,5-trifluoro-6-hydroxypyrazine (851), 2-chloro-6-hydroxy-3,5-diphenylpyrazine (873), 2-chloro-6-hydroxy-5-methyl-3-phenylpyrazine (873), 2-chloro-6-hydroxy-3-methyl-5-phenylpyrazine (873), 5,6-dichloro-1 -cyclohexyl-34iydroxy-2-oxo-l, 2-dihydropyrazine (853), 2-chloro-5-hydroxy-3-methoxy-6-methoxycarbonylpyrazine (881), 2-(4 -amino-3, 5 -dibromo-phenylsulfonamido)-3Tiydroxy-6-methoxypyrazine (881), 2-amino-3-hydroxy-... 

Dinitro-phenylthio)- 848 3-Ethylsulfonyl- 1733 3-(Fluoro-acetoxy)- 1870, 1933 3-Hydroximino- 1246 3-(2-Hydioxy-ethyl)-2,3,5-trimethyl- 853 5-Hydroxy-3-methoxy- 1957 5-(3-Hydroxy-l-octinyl)-3-[5-(2-methoxycarbonyl-... 

Diese Nachteile konnen durch Methylierung4 7 bzw. Acetylierung8 der phenolischen Hydroxy-Gruppe iiberwunden werden. Die Tab. 15 (S. 167) gibt einen Oberblick iiber ei-nige aus Hydroxy-, Methoxy- und Mercapto-carbonsauren durch Reduktion mit Lithiumalanat hergestellten Alkohole. 

Tab. 15 Alkohole durch Reduktion von Hydroxy-, Methoxy- und Mercapto-carbonsauren...

Cieplak stated that the lone pair back-donation of C5 substituent also stabilizes the transition state during the syn approach since it improves hyperconjugation of the C5-H bond (extended hyperconjugation). He pointed out that for the cyclopen-tadienes having C5 substituents such as hydroxy, methoxy, amino, and chloro moiety, the hyperconjugative stabilization and the back-donation work in the same direction (Scheme 27). 

Lithiated chiral oxazolines have been shown to react with various electrophiles, generating a new asymmetric center with considerable bias. This process has led to the synthesis of optically active a-alkylalkanoic acids,47 n-hydroxy(methoxy)alkanoic acids,48 / -hydroxy(methoxy)alkanoic acids,49 n-substituted y-butyrolactones,50 and 2-substituted-l,4-butanediols (Fig. 2-4).50... 

Electron-donating groups (amino, methylamino, hydroxy, methoxy) in the 2-position, on the other hand, are extremely undesirable because, unlike similar substituents in the 1,4-positions, they are unable to form intramolecular hydrogen bonds with the keto groups of anthraquinone and hence are highly susceptible to photo-oxidation [167]. 

COMT = Catechol-O-Methyl transferase MAO = Monoamine Oxidase HMMA = Hydroxy Methoxy Mandelic Acid... 

Natnre does not actually make a methylenedioxy group using formaldehyde. Instead, it modifies an existing ortAo-hydroxy-methoxy arrangement. Enzymic hydroxylation of the methoxy methyl converts this substitnent into what is identical to a hemiacetal of formaldehyde, and then acetal formation follows in a process analogous to a chemical synthesis. The hydroxylating enzyme involved is a cytochrome P-450 mono-oxygenase (see Box 11.4). 

These results are explained in terms of coordination of the nucleophilic hydroxy-(methoxy-, silyloxy-, amino-) functionality of the stereogenic center with the incoming electrophilic singlet oxygen (Scheme 24, right side, transition states C). Stereodifferentiation results from the preferred conformation of the ally lie alcohol for oxygen transfer, which is mainly determined by 1,3-allylic strain (threo-C favored over erythro-C). The experiments also showed that the optimal dihedral angle of the allylic alcohol (C=C—C—O) in the transition state lies between 90° and 130° and the newly formed double bond in the... 

Strong electron-releasing substituents, such as hydroxy, methoxy, or acetylamino groups, generally promote electrophilic substitution in the same ring. The electrophilic substitution of dibenzofurans with such a... 

Flavanones with Hydroxy, Methoxy, and Methylenedioxy Substituents Reported from 1992 to 2003... 

Flavanone aglycones bearing hydroxy, methoxy, and methylenedioxy substituents only... 

Interestingly, when carboxylate derivatives are considered, the SET process is irreversible (due to release of CO ) and the degradation rate is maximum when this mechanism is supposed to be operating. On the contrary, when a radical cation or a semiquinone intermediate is invoked, as in the case of quinoline or hydroxy-methoxy-chloro benzenes [60,64], the rate is minimum due to the back reaction. 

This method, which is applicable to mono-, di-, tri-, and tetraalkyl as well as phenyl-substituted olefins, gives almost complete Markovnikov addition. Hydroxy, methoxy, ace-toxy, halo, and other groups may be present in the substrate without, in general, causing difficulties.147 When two double bonds are present in the same molecule, the use of ultrasound allows oxymercuration of the less-substituted one without affecting the other.148... 

The oxidation of 1,7-phenanthrolines containing a hydroxy, methoxy, or amino group in the 5- or 6-position to 1,7 phenanthroline-5,6-dione (51) by nitric acid has been patented.249 250 Its monosemicarbazone has also been patented.251 l,7-Phenanthroline-5,6-dione (51) gives the diepoxide (52) on reaction with diazomethane.226... 

There has been considerable interest in the preparation of 4,7-phenanthroline-5,6-dione and its relatives due to their antibacterial activity. Patents225,249, 250,256,257 have appeared covering the oxidation of 5- or 6-substituted hydroxy-, methoxy-, or amino-4,7-phenanthrolines to... 

The Effect of Hydroxy, Methoxy and Methylenedioxy Groups on the Ultraviolet Spectra of Aromatic and Heterocyclic Compounds — Alkaloids F. Santavy, Heterocycles, 1980, 14,1159-1172. 

Substitution of a Hydroxy, Methoxy, or Amino Radical at the Amino Group of Cytosine Tautomeric Shift 2 — 6... 

Cytosines substituted at the amino group by hydroxy, methoxy, or amino groups are known to exist as mixtures of tautomers 21 or 23 and 22 or 24, respectively. The tautomeric properties of these cytosines were... 

Alkyl and (or) halobcnzofuranones References Acetoxy-, hydroxy-, methoxy- benzofuranones References... 

Caffeic acid is metabolized by liver enzymes to give ferulic, vanillic acids and their glycine conjugates, which may be excreted into urine. In addition, dihydroferulic acid is produced by catechol o-methyltransferase in the liver. Because of the specificity of this enzyme, only ortho hydroxy-methoxy metabolites may be formed. These reactions may occur in rats as well in humans [15]. Fig. (2) shows the metabolic reactions of caffeic acid in body tissues. 

These compounds are differentiated primarily by the oxidation state of the central three carbon atom unit. Thus, as shown in Figure 1, some compounds are classified as flavones, flava-nones, flavonols, anthocyanins, etc. (The A and B rings have been left off for clarity). A secondary means of differentiating flavonoids is by the position and numbers of attached hydroxy, methoxy or sugar units. In citrus, flavonoids usually occur as glycosides, although the polymethoxylated flavones are a notable exception. 

The oxidative cyclization of an ortho-hydroxy-methoxy-substituted aromatic system giving a methylenedioxy group is also known to involve a cytochrome P-450-dependent mono-oxygenase. This enzyme hydroxylates the methyl to yield a formaldehyde hemiacetal intermediate, which can cyclize to the methylenedioxy bridge (the acetal of formaldehyde) by an ionic mechanism (Figure 2.21). 

Fig. 11 Different types of 2-bromo-3-hydroxy/methoxy-phospholane-based glycosyl donors (105 I and 11/111 III and IV)...

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