3-Hydroxy-4-methoxybenzoic acid

To a solution of 10.0 g 2-hydroxy -methoxybenzoic acid (59.5 mmol) and 8.0 g NaOH (200 mmol) in 90 mL water at 10°C was added a solution of 17.0 g potassium persulfate (62.9 mmol) in 300 mL water over a 4-h period. The reaction mixture was then allowed to warm to room temperature and was stirred for 24 h, resulting in a purple solution. The mixture was neutralized with 1 N hydrochloric acid and extracted with ether (3 x 150 mL). The combined organic extracts were washed with brine and dried over MgS04. Concentration and recrystallization from ethanol and water afforded 3.21 g 2,5-dihydroxy-4-methoxybenzoic acid as colorless rectangular rods, in a yield of 30%, m.p. 200-202°C (dec). 

Chromones are readily oxidized by permanganate or dichromate with opening of the pyran ring and the formation of a salicylic acid (402). Flavones and isoflavones are also degradatively oxidized for example oxidation of munetone (403) with alkaline hydrogen peroxide yields 2-methoxybenzoic acid and 4-hydroxy-2-isopropylbenzofuran-5-carboxylic (isotubaic) acid. 

By appropriate choice of the reactants and the reaction conditions, a phenol-substituted carboxylic acid may react with an organotin compound to give both an organotin ester and an organotin aryl oxide within the same molecule. The reaction of trimethyltin chloride with 4-hydroxy-3-methoxybenzoic acid (HVAH) in the presence of water and pyridine at 130 °C in a sealed tube gave the unique two-dimensional coordination polymer 134 (equation 2)286. 

One great advantage of the decarboxylative halogenation with O-acyl esters of A-hydroxy-2-thiopyridone is that the reaction does not require any heavy metal such as Ag or Hg, unlike the Hunsdiecker reaction [24, 25]. Moreover, decarboxylative bromination of p-methoxybenzoic acid can be also carried out in good yield, while it does not proceed with the Hunsdiecker reaction instead, electrophilic bromination on the aromatic ring occurs. 

The phenolic acids of interest here [caffeic acid (3,4-dihydroxycinnamic acid), ferulic acid (4-hydroxy-3-methoxycinnamic acid), p-coumaric acid (p-hydroxycinnamic acid), protocatechuic acid (3,4-dihydroxybenzoic acid), sinapic acid (3,5-dimethoxy-4-hydroxyxinnamic acid), p-hydroxybenzoic acid, syringic acid (4-hydroxy-3,5-methoxybenzoic acid), and vanillic acid (4-hydroxy-3-methoxybenzoic acid)] (Fig. 3.1) all have been identified as potential allelopathic agents.8,32,34 The primary allelopathic effects of these phenolic acids on plant processes are phytotoxic (i.e., inhibitory) they reduce hydraulic conductivity and net nutrient uptake by roots.1 Reduced rates of photosynthesis and carbon allocation to roots, increased abscisic acid levels, and reduced rates of transpiration and leaf expansion appear to be secondary effects. Most of these effects, however, are readily reversible once phenolic acids have been depleted from the rhizosphere and rhizoplane.4,6 Finally, soil solution concentrations of... 

Vanillic acid (= 4-Hydroxy-3-methoxybenzoic acid) (phenolic acid)... 

In another study, the substrate was 3,4-dihydroxybenzoic acid, and the reaction products were 3-methoxy-4-hydroxybenzoic acid and 3-hydroxy-4-methoxybenzoic acid. The substrate and the two products were separated by HPLC on a reversed-phase column (LiChrosorb) with a mobile phase of 0.05 M acetic acid in methanol-water (1 4, v/v), pH 3.2 Figure 9.12 shows the separation obtained under these conditions. 

C8H802 methyl benzoate 93-58-3 472.65 44.023 1,2 13498 C8H804 3-hydroxy-4-methoxybenzoic acid 645-08-9 543.15 48.045 2... 

It is a relatively recent observation that Colchicum species contain numerous chemical constituents of diverse chemical properties. Recognition of this fact has led to more efficient methods of isolation. In addition to neutral, phenolic, and basic alkaloids, 0. autumnale contains fatlike substances which are removed by a preliminary ligroin extraction of the pulverized, dry material. From such an extraction of the flowers of C. autumnale, Santavy and Herout (293) have isolated a paraffin, Ca7-28H5g 58, m.p. 58-60° an alcohol, CaaH450H, m.p. 66-67° and a phytosterol, m.p. 139-140°. Benzoic, salicylic, and 2-hydroxy-6-methoxybenzoic acids may be separated from the alkaloid mixture by virtue of their solubility in ether and aqueous base (294). The alkaloids themselves may be separated into neutral, phenolic, or basic fractions by standard extraction techniques. Pure alkaloids may be obtained from each fraction by fractional crystallization and chromatography on... 

H.74) Benzoic acid, 4-hydroxy-3-methoxy-, 4-hydroxy-3-methoxybenzoic acid, p-vanillic acid, vanillic acid, 4-hydroxy-m-anisic acid [121-34-6]... 

A range of simple analogs of benzoic acid and phenylalanine, easily obtainable from standard chemical suppliers, were chosen as substrates. These included a large number of hydroxy- and dihydroxybenzoic acids, aminoben-zoic acids, nitrobenzoic acids, fluoro-, difluoro-, trifluoro-, tetrafluoro- and pentafluorobenzoic acids, chlorobenzoic acids, iodobenzoic acids, and methoxybenzoic acids. A number of structures other than those with a six-mem-bered aromatic ring were also tried, including pyridinecarboxaldehydes, alicy-clic carboxylic acids, naphthalenecarboxylic acids, furancarboxylic acids, thiophenecarboxylic acids, nitro-, bromo-, and chlorothiophenecarboxyhc acids. 

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