5-Hydroxy-2-hydroxymethyl-4-pyrone

Kojic Acid, 5-Hydroxy-2-(hydroxymethyl)-4H-py-ran-4-one 5-hydroxy-2-(hydroxymethyl)-4-pyrone 2-hydroxymethyl -5 -hydroxy-> -pyrone. mol wt 142.11. 

Hydroxy-2-hydroxymethyl-4-pyrone (kojic acid) ("Other values on Vol.3, p.259)... 

N-[2-Hydroxy-1 -(hydroxymethyl) pentadecyl] hexadecanamide. See Palmitamidohexadecanediol 5-Hydroxy-2-(hydroxymethyl)-4H-pyran-4-one 5-Hydroxy-2-(hydroxymethyl)-4-pyrone. See Kojic acid... 

Complexes or chelates with M R 1 1 are formed in the range up to pH 4 - 4,5 following equilibria with Kojic acid (5-Hydroxy-2-hydroxymethyl--4-pyron) ... 

The thick interfacial layer and the viscous or gelled aqueous phase might have some advantages when protection of sensitive addenda is required. Kim et al. (2003) treated the internal aqueous phase with hydroxypropyl-beta-cyclodextrin (to make the internal aqueous phase more hydrophilic) and introduced kojic acid (5-hydroxy-2-(hydroxymethyl)-4-pyrone) as a model antioxidant. The multiple emulsions were also stabilized sterically by addition of xanthan gum into the external aqueous phase. The authors found improved stability against coalescence and improved chemical stability. The stability of kojic acid could be maintained at 90% for 10 weeks (Figure 5.13). 

Fig. 12. 600-MHz NMR spectra of (A) Streptomyces antibioticus Met tyrosinase in 100 mM sodium phosphate, pH 6.8, at 280 K (B) same as (A) but in the presence of 500 mM NaCl (C) same as (A) but in the presence of 2 mM 2-hydroxymethyl-5-hydroxy-y-pyrone (kojic acid). Asterisks indicate the N8H of the six coppercoordinating histidine residues. Reprinted with permission from Bubacco et al. (2000).

The allylalkohol 6 turns out to be the obvious precursor of the protected diol 5, and 6 reasonably arises from a Shapiro coupling of cyclohexadienyllithium 7 with the cyclohexene-4-aldehyde 8 which is the product of oxidation and subsequent diol protection of the bicyclic hydroxylactone 9 the latter emerges from rearrangement of the Diels-Alder cycloadduct 13 of 3-hydroxy-2-pyrone 14 as the diene and 4-hydroxy-2-methyl-2-butenoate 15 as the electron-deficient dienophile. The cyclohexadienyllithium 7 originates from the sulfonylhydrazone of the ketone 10 which is, once again, a Diels-Alder cycloadduct of the protected 3-hydroxymethyl-2,4-dimethyl-l,3-pentadiene 12 and ketene 11 as the dienophile. 

Kojic acid is 2-hydroxymethyl-5-hydroxy-Y-pyrone, an excellent free-radical scavenger. It is usually produced by solid-state fermentation of starchy substrate by Aspergillus species. Media containing simple sugars such as glucose, sucrose, or fructose as carbon source... 

Kojic acid (J2-dihydro-3-hydroxy-6-hydroxymethyl-y-pyrone) ... 

Kojic acid (Figure 37.35, also known as 5-hydroxy-2-(hydroxymethyl)-4H-pyran-4-one and 5-hydroxy-2-(hydroxymethyl)-l,4-pyrone, is a tyrosinase inhibitor... 

Further validation of the mechanism proposed for the catecholase activity of the dicopper complexes [Cu2(L66)]" , [Cu2(L55)], and [Cu2(EBA)]" " (Scheme 17) has been obtained investigating the inhibitory effect of kojic acid [5-hydroxy-2-(hydroxymethyl)-y-pyrone] (154). This fungal metabolite is one of the most efficient inhibitors of mushroom tyrosinase and other polyphenol oxidases (160,161). When the catalytic oxidation of DTBCH2 was studied in the presence of kojic acid, strong competitive inhibition was observed in the steps exhibiting substrate concentration dependence,... 

Treatment of MI-220 or MI-221 (R = H, CH3) with aromatic amines in water gives l-aryl-5-hydroxy(or methoxy)-4-pyridone-2-carboxylic acids, which are readily decarboxylated to XII-223, (R = H, CH3) or converted to ethyl esters."" 2-Hydroxymethyl-S-methoxy-4-pyrone, a monomethyl ether of kojic acid, and 2-dialkylaminoethylamines in water give l-(2-dialkylaminoethyl)-2-hydroxymethyl-5-methoxy-4-pyridones (MI-224 R = CH3,C2Hs). Natural maltol glucoside and ammonia or primary amines give the corresponding pyridones (XU-225) when boiled in methanol. ... 

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