Methyl 4-hydroxybenzoate, reaction with

Reaction of n-butylamine with methyl salicylate in dioxane is second-order in amine (Snell et al., 1967), but reaction with methyl p-hydroxybenzoate could not be detected. The aminolysis of phenyl... 

Protection of carboxylic acids. The 2-(2-pyridyl)ethyl group is useful for protection of amino acids. The esters are obtained by reaction with 1 and DCC/1-hydroxybenzo-triazole. The group provides higher solubility in protic solvents, and is stable to both acids and bases. It is removed by treatment with methyl iodide and a weak base. 

Several papers report new findings on ubiquinone biosynthesis. A mitochondrial membrane-rich preparation from baker s yeast can convert 4-hydroxybenzoate and isopentenyl pyrophosphate into the ubiquinone precursor 3-all-trans-hexaprenyl-4-hydroxybenzoate (234). Details of the cell-free system are presented. With preformed polyprenyl pyrophosphates, the system catalysed the polyprenylation of several aromatic compounds, e.g. methyl 4-hydroxybenzoate, 4-hydroxybenzaldehyde, 4-hydroxybenzyl alcohol, and 4-hydroxycinnamate. No evidence was obtained for the involvement of 4-hydr-oxybenzoyl-CoA or 4-hydroxybenzoyl-S-protein in the reaction. With shorter-chain prenyl pyrophosphates a shorter prenyl side-chain was introduced, e.g. geranyl and farnesyl pyrophosphates gave products with a 3-diprenyl and 3-triprenyl side-chain respectively. A crude enzyme preparation from E. coli... 

An additional method of ACEC synthesis was based on hydroxybenzoic acids as the starting materials [32]. The synthesis starts from esterification of the acid with 3-cyclohexenyl-1-methyl alcohol. The following hydroxybenzoic acids were used 2-hydroxybenzoic (salicylic), 2,4-di-hydroxybenzoic ( 3-resorcylic) and 3,4,5-trihydroxybenzoic (gallic) acid. The phenolic hydroxyls in the cy-clohexenylmethyl esters were transformed in glycidyl ethers in the usual way (reaction with excess ECH followed by dehydrochlorination). Eventually, epoxidation with PAA was carried out (Scheme 51). The epoxide groups content in the ACECs thus prepared was above 85% of the calculated value. 

Another MOF constructed from Cu paddlewheel SBUs and with 5-nitro-1,3-benzenedicarboxylate as the ligand can be used for the acetylation of methyl 4-hydroxybenzoate with acetic acid anhydride. The framework did not remain intact upon exposure to acetic acid, one of the reaction products [53]. 

Methylphenol is carboxylated to 2-methyl-4-hydroxybenzoate by a methanogenic-enrich-ment culture before degradation to acetate (Figure 8.44a) (Roberts et al. 1990) C-labeled bicarbonate prodnced carboxyl-labeled acetate, while C-methyl-labeled 3-methylphenol yielded methyl-labeled acetate. However, 2-methylbenzoate formed by dehydroxylation of 2-methyl-4-hydroxybenzoate was not further metabolized (Figure 8.44b). A similar reaction occnrs with a sulfate-reducing mixed culture (Ramanand and Suflita 1991). 

This enzyme [EC 1.14.99.15] catalyzes the reaction of 4-methoxybenzoate with AH2 and dioxygen to produce 4-hydroxybenzoate, formaldehyde. A, and water. The bacterial enzyme consists of a ferredoxin-type protein and an iron-sulfur fiavoprotein (FMN). 4-Ethoxyben-zoate, A-methyl-4-aminobenzoate, and toluate can serve as substrates as well. The fungal enzyme acts best on ver-atrate. 

The reaction of methyl thiosalicylate with DMAD yields the Michael adduct (358), which undergoes cyclization on ammonolysis to give methyl 3-hydroxybenzo[fc]thiophene-2-carboxylate (360) through the postulated intermediate 359 (Scheme 55). On the other hand, the reaction of o-mercaptobenzamide with DMAD gives a 1 1 adduct (193) which is converted in the presence of base into the l,3-benzothiazin-4-one derivative (194) [Eq. (31)]. In the reaction of methyl... 

With respect to the oxygenation of methyl 4-hydroxybenzoate (as its tetra-n-butylammonium salt) to methyl 3,5-dihydroxybenzoate, remarkable differences in activity for this test reaction were observed with the three ligand sys-... 

Esterification is frequendy carried out by direct reaction of the carboxylic acid with an alcohol in the presence of a small amount of mineral acid, usually concentrated sulfuric or hydrochloric acid. The esters of commercial importance in both 0- and -hydroxybenzoic acid are the methyl esters. Direct esterification has the advantage of being a single-step synthesis, but being an equilibrium it is easily reversed. The reaction to the ester is driven by either of... 

After oral administration of caffeic acid to rats, small amounts of vanillic acid and vanilloylglycine are excreted. The conversion of p-hydroxycinnamic acid into /7-hydroxybenzoic acid is found in rat liver mitochondria [18], Studies with /7-hydroxy[U-14C]cinnamic acid have showed that 14C02 is released during reaction, indicating that reaction probably followed the p-oxidation type reactions, the two carbon being first removed as acetyl-CoA, and then oxidized to C02. It is assumed that conversion of ferulic acid formed by methylation of caffeic acid into vanillic acid occurs in rat liver mitochondria. 

This group of chemicals, which are found naturally in many fruits, are used as preservatives, a function that they also perform within fruit. Benzoic acid itself may be used, or more commonly sodium benzoate (a salt) or ethyl or methyl para-hydroxybenzoate, also known as parabens. They have sometimes associated with adverse effects. Anaphylaxis-like reactions have been reported as well as urticaria. About 4 per cent of people who suffer from asthma may experience breathlessness and wheezing when exposed to benzoates. Parabens are often used as preservatives cosmetics. 

The steroidal dienone (170) can be induced to undergo the relatively unusual reorganization to the 2-hydroxy-4-methylandrosta-l,3,5-triene (171), by irradiation in refluxing acetic acid although only 48% of the acetate (171) was isolated, the related 17-ketone (36%) was also formed. The p-dienones (172) and (173) are restructured on irradiation in cyclohexane with net relocation of methyl and t-butyl groups to afford the phenols (174) and (175) in 55% and 73% yield, respectively. A photo-induced aryl shift in the benzylisoquinoline dienone (176) was employed to prepare the aporphine (177 44%) en route to ( )-boldine. The p-dienones (178 X = Cl, X = Ns) aromatize on irradiation to yield the alkylated p-hydroxybenzoates (179 e.g. X = Ns, 57%) as well as minor quantities, of their isomers (180). Mechanistic aspects of these reactions are discussed in the literature cited. 

Phenol readily couples with diazonium salts to yield coloured compounds. The latter can be nsed for the photometric detection of phenol as in the case of diazotized 4-nitroaniline. Sahcylic acid (2-hydroxybenzoic acid) can be prodnced by the Kolbe-Schmitt reaction (stndied by the density functional method ) from sodinm phenolate and carbon dioxide, whereas potassium phenolate gives the para compound. Alkylation and acylation of phenol can be carried out with aluminium chloride as catalyst methyl groups can also be introduced by the Mannich reaction. Diaryl ethers can only be produced under extreme conditions. 

The classical Kolbe-Schmidt reaction treats alkali metal phenoxides and carbon dioxide at higher than atmospheric pressure, giving salicylic acid. Hirao and Kato developed several modifications for industrial production ". Recently, phenol phosphate was enzymatically carboxylated, giving p-hydroxybenzoic acid ". As for related reactions, Sartori and coworkers conducted o-carbamoylation of aluminum or boron phenoxides with alkyl isocyanate ", and Adachi and Sugasawa o-cyanated phenols using methyl thioisocyanate in the presence of BCI3 (equation 54). ... 

The second example of an acylation during which the acid chloride is generated in situ (67BCF88) (Scheme 12) involves the reaction of 4-aminopyrazol-3-one 30 with 2-hydroxy-5-(methoxycarbonyl)benzoic acids 47a c where phosphorus trichloride is used and gives methyl 3- [(3-oxopyrazol-4-yl)amino]carbonyl -4-hydroxybenzoates 48a c. 

Methyl 10-hydroxybenzo[6]naphtho[2,3-e][l,4]dioxine-8-carboxylate, synthesised from the reaction of 1,2-dihydroxybenzene and 3,4-difluorobenzaldehyde and subsequent Stobbe condensation, is a source of [l,4]benzodioxinonaphtho[l,2-6]pyrans. Similarly, using 2-benzoyl[l,4]benzodioxine in the Stobbe reaction enables indeno analogues to be obtained (Scheme 21) <03USP0168645>. With appropriate gem diaryl substitution in the pyran ring, these molecules show two absorption peaks between 440 - 610 nm and are fast fading. 

In a comprehensive study of 2-multiprenylphenols which are involved as biosynthetic precursors of ubiquiniones, three approaches were adopted (ref.6). In the first, to avoid 4-substitution found in acid-catalysed reaction of phenol, a blocking 4-methoxycarbonyl group was used. Thus reaction of methyl 4-hydroxybenzoate with phytol in dioxane containing boron trifluoride etherate at 50°C afforded a low yield of methyl 4-hydroxy-2-phytylbenzoate which upon hydrolysis and decarboxylation gave 2-phytylphenol. 

In the C20 series the 2-phytyl intermediate from the reaction of methyl 4-hydroxybenzoate with phytol, by treatment with hot methanolic hydrogen chloride afforded a chroman, namely 6-methoxycarbonyl-2-methyl-2-(4 ,8, 12 -trimethyldecyl)chroman (ref. 6). 

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