Pyrazine, tetramethyl

Pyrazines are generally associated with nonenzymatic browning. However, pyrazines have also been found as a result of microbial action. Bacillus subtilis was the first organism found to produce a pyrazine (tetramethyl pyrazine [105]). Since that time, several pyrazines (2-acetyl, dimethyl, 2-methoxy-3-ethyl, 2,5 or 2,6-diethyl-3-methyl, trimethyl, tetramethyl, and trimethyl pyrazine) have been identified in aged cheese [16,106-109]. While some of these pyrazines may be formed via the Maillard reaction during aging of the cheese, it is likely that they were formed via microbial action. 

Coronary blood flow increased Pyrazine, tetramethyl- 2-N heterocyclic alkaloid 1137... 

In einem Elektrolyt aus Methanol und verdiinnter Natronlauge werden 2,3-Diphenyl-(—1,4 V)5 und 2,3,5,6-Tetramethyl-pyrazin (—1,3 V)6 zu 2,3-Diphenyl-1,2-dihydro-bzw. 2,3,5,6-Tetramethyl-l,2-dihydro-pyrazin reduziert ... 

HPA = (4-pyridylthio)aceticacid 2-fur = 2-furoate a-fur = a-furoate = ([Pg.116]

Interatomic distances as calculated from the analysis of the rotational fine structure of the ultraviolet spectrum are C-C, 1.395 A C-N, 1.341A and C-H, 1.085 A.66 These are very similar to the bond lengths for pyridine which are C-2-C-3, 1.3945 A C-3-C-4, 1.3944 A and C-2-N, 1.3402 A. The C-N-C bond angle in pyrazine is 115° and the C-C-N bond angle 122.5°.56,67 A delocalization energy for pyrazine of ca. 18 kcal/mole is indicated from heats of combustion data.68 The C=N bond energy in 2,2,5,5-tetramethyl-2,5-dihydropyrazine has been calculated to be 130.3 kcal.58a... 

Methylated 1,4-dihydropyrazines (1,2,4-tri-, 1,2,4,5-tetra-, and 1,2,4,6-tetramethyl) as well as imidazolines have been isolated from the reaction of sucrose with methylamine at high temperatures (120°-260°), for prolonged reaction periods (18 hours) and in the presence of ammonium phosphate as catalyst. 1,4-Dihydropyrazines are also isolated from the reaction of sucrose and ethanolamine sucrose-ammonia interaction yields a wide range of pyrazines and imidazoles.369-372... 

Heating either trimethyl 2-methyl-6-ethylidene-2,6-dihydro-l//-pyrido[l,2a]-pyrazine-7,8,9-tricarboxylate or tetramethyl 1,2-dimethyl-2,9a-dihydro-l//-pyrido-[l,2-a]pyrazine-6,7,8,9-tetracarboxylate in dilute HC1 gave dimethyl 2-methyl-7-propionyl-l,6-dioxo-2,6-dihydro-l//-pyrido[l,2-a]pyrazine-8,9-dicarboxylates (62JCS1510). 1,12-Dihydroxyper-hydrodibenzo[ac]pyrazine was prepared from l-(2-tetrahydrofuryl)-9-hydroxyperhydropyrido[l,2-a]pyrazine in AC2O saturated with HBr at 95-100°C (61BSF2135). 

The 1,5-quinonoid 6,6,7,7-tetramethyl-6,7-dihydro-8f/-pterin (146) reveals interesting reactivity towards nucleophiles due to the blocked 6-position. Solvolysis with OH leads via ring contraction to 2-amino-5,5,6,6-tetramethyl-5,6-dihydroimidazo(4,5-6)pyrazine (145) and O-methylhydroxyl-... 

Pyrazin 2,5-Diethoxy- E9b/2, 295 ( — H2 -> Hetaren) Pyrazin-l,4-bis-oxid Tetramethyl-E9b/2, 305 (N-Bis-oxidation) Pyrazin-l-oxid 3,6-Diethyl-2-hydroxy- E9b/2, 312 (4-Oxid-Red.)... 

TETRAMETHYL PYRAZINE (FCC) see TDU800 TETRAMETHYL SIUCATE see MPI750 TETRAMETHYLSILIKAT see MPI750 TETRAMETHYLSTANNANE see TDV750 TETRAMETHYLSUCCINONITRILE see TDW250... 

Cocoa Butter Cocoa butter is one of the most Uked and highly prized food ingredients because of its desirable flavor and unique melting behavior. As early as 1961, van Elzakker and van Zutphen (32) studied and identified 23 volatile compounds in the vacuum steam distillate of cocoa butter. Later, Rizzi (33) identified nine alkylpyrazines including methylpyrazine, 2,5-dimethylpyrazine, 2,6-dimethylpyrazine, 2,3-dimethylpyrazine, 2-ethyl-5-methylpyrazine, trimethylpyra-zine, 2,5-dimethyl-3-ethylpyrazine, 2,6-dimethyl-3-ethylpyrazine, and tetramethyl-pyrazine in the basic fraction of a vacuum steam distillate of cocoa butter. 

The parent compound of this series, pyrazine, was first prepared in trace amounts by Wolff (30) by heating aminoacetaldehyde diethyl acetal [H2NCH2CH(OEt)2] with anhydrous oxalic acid at 110-190°C, and later in better yield by heating the mercuric or platinic chloride double salts (of the aminoacetaldehyde acetal) with hydrochloric acid (31) it was also obtained from aminoacetaldehyde with mercuric chloride in sodium hydroxide (23). Wolff in 1893 (22) also prepared pyrazine by decarboxylation of the tetracarboxylic acid, obtained by oxidation of tetramethyl-pyrazine and Stoehr (32) prepared it by the distillation of piperazine with lime and zinc dust. Brandes and Stoehr (33) in 1896 described the preparation of pyrazine by heating glucose with 25% aqueous ammonia at 100°C. 

---