2- pyridine, reaction furanones

Benzoylation of D-g/ycero-D-gw/o-heptono-1,4-lactone with an excess of benzoyl chloride and pyridine afforded the hept-2-enono-1,4-lactone as the main product (198). The di- and triunsaturated compounds were isolated in very low yield from the mother liquors (199). Higher yields of the di- and triunsaturated derivatives 153 and 154 were obtained when the /5-elimination reaction was performed with triethylamine on the previously synthesized per-O-benzoyl D-g/ycero-D-gw/o-heptono-1,4-lactone. Employing 10% triethylamine in chloroform, the lactone 153 was obtained as an E, Z dias-tereomeric mixture in 9 11 ratio as determined by H n.m.r. When 20% triethylamine was used, the furanone 154 was obtained in 59% yield (200). Its structure was assigned, on the basis of H and 13C n.m.r. spectra, as 3 -benzoyloxy - (5Z)-[(Z)-3 - benzoyloxy - 2 - propenyliden] -2(5 H)- furanone. The stereochemistry of the exocyclic double bonds was established (201) by nuclear Overhauser effect spectroscopy (NOESY). 

A maltol-ammonia browning reaction produced thirteen pyrazines, two pyrroles, two oxazoles, and one pyridine (12). The major products of this system were 2-ethyl-3-hydroxy-6-methylpyridine and 2-ethyl-3,6-dimethylpyrazine. It is difficult to construct possible formation mechanisms for these compounds from maltol and ammonia. All the carbon atoms must come from maltol. It is possible, then, that maltol degrades into smaller carbon units and that these fragments recombine to form larger carbon units, producing these compounds. Recently, the formation of thiophenones and thiophenes from the reaction of 2,5-dimethyl-4-hydroxy-3(2H)-furanone and cysteine or cystine was reported (13. 14). All these reaction mixtures were reported to possess a cooked meat-like flavor. 

Stereoselective trans a-hydroxylation of (5)-dihydro-5-(t-butyldiphenylsiloxymethyl)-2(3/f)-furanone can be realized in good yield by enolization and reaction with the Oxodiperox-ymolybdenum(pyridine)(hexamethylphosphoric triamide) complex (MoOPH) (eq 10). Appropriate manipulation of the resulting trans-hydroxylactone provides 1,3-polyols typified by (18), as well as tetrahydropyran (19) which is a key intermediate in mevinic acid syntheses. ... 

The Maillard reaction between reducing sngars and amino acids under specific conditions (pH, water activity, and temperature) is primarily responsible for the production of heterocyclic volatile compounds such as pyrazines, pyridines, pyrroles, furans, and the Strecker aldehydes. Maillard reactions produce many potent aroma compounds identified in some roasted tree nuts, including 3-methylbutanal, 2,3-butanedione, methional, phenylacetaldehyde, 2-ethyl-3,5-dimethylpyrazine, and 2,5-dimethyl-4-hydroxy-3(2//)-furanone, among others. 

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