4-Hydroxy-5-methyl-3 -furanone formation

The formation of oxygen-containing heterocyclic compounds is also a consequence of the Maillard reaction. Amines and amino acids have a catalytic effect upon the formation of 2-furaldehyde (5), 5-(hydroxy-methyl)-2-furaldehyde (11),2-(2-hydroxyacetyl)furan (44),2 and 4-hy-droxy-5-methyl-3(2//)-furanone (111) (see Ref. 214). This catalytic effect can be observed with several other non-nitrogenous products, including maltol. The amino acid or amine catalysis has been attributed to the transient formation of enamines or immonium ions, or the 1,2-2,3 eno-lization of carbohydrates. Of interest is the detection of A -(2-furoyl-... 

Scheme 22.—Mechanism for the Formation of 4-Hydroxy-5-methyl-3(2/f)-furanone.

An effort has also been made to determine the structure of products providing coloration in the Maillard reaction prior to melanoidin formation. The reaction between D-xylose and isopropylamine in dilute acetic acid produced 2-(2-furfurylidene)-4-hydroxy-5-methyl-3(2/f)-furanone (116). This highly chromophoric product can be produced by the combination of 2-furaldehyde and 4-hydroxy-5-methyl-3(2//)-furanone (111) in an aqueous solution containing isopropylammonium acetate. The reaction between o-xylose and glycine at pH 6, under reflux conditions, also pro-duces " 116. Other chromophoric analogs may be present, including 117,... 

From the reaction of D-ribose-J-14C with secondary amine salts in aqueous acid, Peer and van den Ouweland215 isolated 4-hydroxy-5-methyl-3(2H)-furanone (120) (11.4%), and found it to be labeled entirely at the methyl carbon atom. Thus, in the presence of amines, the formation of 120 must proceed through the 1-deoxydiulose by the mechanism described in Section II (see p. 168). In contrast, the reaction of D-ribose-J-14C 5-phosphate218 gave 120 having no radioactivity in the methyl carbon atom, from which it was concluded that the methyl carbon atom originates from C-5 of the D-ribose. The... 

The routes involved in the formation of the various furan sulphides and disulphides involve the interaction of hydrogen sulphide with dicarbonyls, furanones and furfurals. Possible pathways are shown in Scheme 12.8. Furanthiols have been found in heated model systems containing hydrogen sulphide or cysteine with pentoses [56-58]. 2-Methyl-3-furanthiol has also been found as a major product in the reaction of 4-hydroxy-5-methyl-3(2H)-furanone with hydrogen sulphide or cysteine [21, 59]. This furanone is formed in the Maillard reaction of pentoses alternatively it has been suggested that it may be produced by the dephosphorylation and dehydration of ribose phosphate, and that this may be a route to its formation in cooked meat [21, 60]. 

Blank, I., Lin, J., Fumeaux, R., Welti, D.H., and Fay, L.B. 1996. Formation of 3-hydroxy-4,5-di-methyl-2(5H)-furanone (sotolone) from 4-hy-droxy-L-isoleucine and 3-amino-4,5-dimethyl-3,4-dihydro-2(5)-furanone. J. Agric. Food Chem. 44 1851-1856. 

Scheme 3.1 Formation of 4-hydroxy-5-methyl-3(2FT)-furanone from a pentose via an Amadori compound and 2,3-enolisation...

The yields of the coloured 2-furfurylidene-4-hydroxy-5-methyl-3(2//)-furanone and 2-furfurylidene-5-methyl-3(2//)-pyrrolinone from xylose and alanine at pH 5 were strongly affected, depending on whether the reaction was carried out at atmospheric pressure or at 400 MPa.109 Formation of both colorants increased progressively... 

Dimethoxy Phenol 3,4-Dimethyl 1,2-Cyclopen tandione 5-Ethyl 3-Hydroxy 4-Methyl 2(5H)-Furanone 3-Ethyl Pyridine Furfuryl Mercaptan Geranyl Isovalerate 2,3 -Heptandione (Z)-3-Hexenyl Butyrate (Z)-3-Hexenyl Formate Hexyl Butyrate Hexyl Hexanoate Isoamyl Isobutyrate Isobutyl Formate Isobutyl Hexanoate Linalool Oxide... 

Furan derivatives have been used to inhibit the formation of melanin when combined with other agents <2000JPP2000302642>. For the group consisting of 5-methyl-2(3//)-furanone 86, 2,5-dimethyM-hydroxy-3(2//)-thiophenone, 2-buten -olide, and 2-hydroxymethylfuran 21, the in vitro formation of tyrosinase was inhibited by... 

Blank, I., Fay, L.B. Formation of 4-hydroxy-2,5-dimethyl-3(2//)-furanone and 4-hydroxy-2(or 5)-ethyl-5(or 2)-methyl-3(2//)-furanone through MaiUard reaction based on pentose sugars. J. Agric. Food Chem. 1996, 44, 531-536. 

Fig, 3,63 Formation of 4-hydroxy-5-methyl-3(2H)-furanone (HMF) from fructose [21]... 

The spiro-dihydrofuran (61) is converted into the cyclobutane derivative (62) under the influence of trifluoroacetic acid. The lithium dienolate (64), derived from the furanone (63), yields solely y-alkylated products on treatment with alkyl halides. Thermolysis of the t-butylperoxybutenolide (65) produces about equal amounts of the hydroxy-furanone (67) and the indenone (68), presumably via the oxide radical (66). Attack of iodide ion on the salt (69) results in the formation of methyl iodide, butanolide, and (surprisingly) methyl 4-iodobutanoate. A description of a study of the photochemical rearrangement of the tetrahydrofurans (70) to the bicyclic oxetans (71) has been presented. ... 

The work also demonstrates that IMP in meat is a precursor for 2-methyl-3-furanthiol and mercaptoketones, although it does not seem to be as important in the formation of 2-furylmethanethiol. The roles of IMP and ribose as sources of these thiols have been discussed previously (12,19). The mechanism involves the Maillard reaction and could require the intermediate formation of 4-hydroxy-5-methyl-3(2H)-furanone and dicarbonyls, such as butanedione and pentanedione, which is then followed by their reaction with hydrogen sulfide or cysteine. The concentrations of IMP in meat vary considerably between different animals and different muscles, and are affected by production conditions both pre- and post-slaughter. The present results indicate that the amount of IMP in the meat at the time of cooking may be an important factor in determining the amount of meaty flavor. 

Fig. 5.16. Formation of 5-ethyl-3-hydroxy-4-methyl-2(5H)-furanone from threonine by heating...

Dehydration of 1-deoxy-l-dibenzylamino-D-fructuronic acid at 100 " C and pH 7 yielded 4-hydroxy-5-methyl-3(2/f)-furanone, a flavouring component of beef. The mechanism of formation of the product was examined using labelled substrates and deuterium oxide. 

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