Pyrazine, 2,3-diethyl-5-methyl

Pyrazine, 2-3-diethyl Sd (roasted) " ° Pyrazine, 2-3-diethyl-5-methyl Sd (roasted) ° ... 

Pyrazine, 2,3-diethyl-5-methyl-, 2,3-diethyl-5-methylpyrazine, 5,6-diethyl-2-methylpyrazine [18138-04-0] FEMA 3336... 

Pyrazine, 6-methyl-2-acetyl Sd Pyrazine, diethyl-dimethyl Sd Pyrazine, methyl Sd (roasted) ... 

Pyrrolidin l-Anilino-2-methyl- E16a, 635 (R2NH 4- R-NH-O- ) Pyrrolo[l,2-a]pyrazin 6-Methyl-l-propyl-3,4-dihydro- E6a, 678 [2-Acyl — 5-CH3 — furan + H2N-(CH2)2-NH2] Pyrrolo l,2-b pyridazin 2,7-Diethyl-3,4-dihydro- E6a, 593 (3,6,9-Undecantrion 4- N2H4)... 

As shown in Fig. 12.1, a 6300-fold increase in potency is observed when the hydroxylic hydrogen is replaced by a diethyl-methyl side chain. A comparable increase in potency is observed in a series of 1-methyl-1,2,3,4-tetrahydro-pyridyl-pyrazines described by Ward et al. exhibiting Mj muscarinic agonists. In changing from O-methyl to O-butyl, the aflSnity for the Mj receptor varies from 850 nM to 17 nM. Another example is found in a series of 2-pyrone-derived elastase inhibitors. ... 

Pyrazine, 2,3-diethyl-. See 2,3-Diethylpyrazine Pyrazine hexahydride. See Piperazine Pyrazine, 2-methyl. See 2-Methylpyrazine 1-Pyrazinylethanone Pyrazin-1-ylethan-1-one 1-Pyrazin-2-yl-ethanone. See 2-Acetyl pyrazine 1H-Pyrazole-3-carboxylic acid, 4,5-dihydro-5-0X0-1 -(4-sulfophenyl)-4-[(4-sulfophenyl) azo]-, trisodium salt. See FD C Yellow No. 5 Tartrazine... 

Our results showed that the flavour profile of peas was affected by market class, cultivar location, and crop year. The highest total volatile compound (TVC) was observed in cultivars from marrowfat-market class. Crops grown in Meath Park location had the highest TVC. Furthermore, different volatile compounds were identified in pea cultivars. In both crop years, cultivars from the green-market class had the highest mean values of esters and hydrocarbons, whereas the highest value of alcohols was observed for the marrowfat-market class, and the dun-market class had the highest mean values of ketones and pyrazine. 3-Methyl-butanol, 1-propanol, 2-ethyl-hexanol, 3-methyl-butanal, trichloromethane, 2-butanone, dimethyl sulfide, ethyl acetate and 2,3-diethyl-5-methyl pyrazine were the most abundant volatile compounds observed in the pea cultivars. 

A tetrahydropyrido[3,4-/)]pyrazine nucleus was constructed from 2,3-dimethylpyrazine 687 by chlorination with A-chlorosuccinimide (NCS) to give 2,3-bis(chloromethyl)pyrazine 688, followed by cyclization with diethyl acet-amidomalonate to pyridopyrazine 689. Hydrolysis and decarboxylation of 689 in hydrochloric acid, then esterification by action of thionyl chloride in methanol gave methyl 5,6,7,8-tetrahydropyrido[3,4-. ]pyrazine-7-carboxylate hydrochloride 690 (Scheme 32) <2003BMC433>. 

Reaction of 4-aryl-7-iodoperhydropyrido]2,l-c][l,4]oxazin-6-ones (07USA2007/0117839, 08WOP2008/013213) and 7-iodo-6-oxo-4-(3,4,5-tri-fluorophenyl)perhydropyrido[2,l-a]pyrazine-2-carboxylate (07USA2007/ 0117839) with P(OEt)3 at 120 °C for 2 h afforded 7-phosphonic acid diethyl esters. 3-Hydroxy-6-arylperhydropyrido[2,l-c][l,4]oxazin-4-ones first were reacted with triphenylphosphonium bromide in refluxing MeCN, then with 3-methoxy-4-(4-methyl-lH-imidazol-l-yl)benzaldehyde at ambient temperature in the presence of NEt3 to provide (Z)-3- l-[3-methoxy-4-(4-methyl-lH-imidazol-l-yl)phenyl]methylidene] derivatives (07USA2007/ 0117798, 08USA2008 /0207900). 

Diethyl-3-methyl pyrazine 2.5- Dime 3 ethyl pyrazine + +... 

The Strecker reactant, i.e., the a-dicarbonyl, picks up ammonia during the Strecker reaction and can then form heterocyclic volatiles, particularly pyrazines. The most powerful odorants among these are the 2-ethyl-3,5-dimethyl- (0.04) and the 2,3-diethyl-5-methyl-derivatives (0.09). It is worth noting that most other alkylpyrazines have much higher thresholds and thus make relatively little contribution to the aroma of heated foods. 

Condensation and cyclization routes continue to be popular for the construction of pyrazines. 2,3-Dihetaryl-6-methylquinoxalines were obtained by condensation of 4-methyl-o-phenyl-enediamine with 1,2-diketones <02JCSP42>. 2,3-Dicyano-5,6-diethyl-1,4-pyrazine (144) was... 

Diethyl-5-methyl-3,6-dihydro-2(l//)-pyrazinone 4-oxide (301) gave dimethyl 4,4-diethyl-3a-methyl-6-oxo-4,5,6,7-tetrahydro-3a/7-isoxazolo[2,3-a]pyrazine-2,3-dicarboxylate (302) (Me02CC CC02Me, CHC13, reflux, 3 h 64%) 544 homologues likewise.544... 

The major volatile components of the pH 9 bait are 2-methyl-propanal, 3-methylbutanal, 2-methylbutanal, methylpyrazine, dimethylpyrazine, ethylpyrazine, 2,3-dimethylpyrazlne, ethylmethyl-pyrazlne, trimethylpyrazlne, dimethylethylpyrazlne, and diethyl-pyrazine. 

Dimethyl-3-ethyl-2-hydroxy-E9b/2, 268f, (Gloxal + H2N-CHR-CO-NH2) 2-Hydroxy-3-isopropyl-5-methyl-E9b/2, 268f. (H3C-CO-CHO + H2N-CHR-CO-NH2) 2-Hydroxy-5(or6)-methyl-3-propyl-E9b/2, 268 f. (H3C-CO-CHO -I- H2N-CHR-CO-NH2) Pyrazin-1,4-bis-oxid 2,5-Diethyl-E9b/2, 309 (N-Oxidat.) Pyrazin-l-oxid... 

The isodiazotate salts (19) of 2-amino-3-methyl- and 3-amino-2,5-dimethyl-pyrazines (17, R =R = H R = Me R = R = Me, R = H, respectively) [prepared from the corresponding amine by refluxing with sodium amide in diethyl ether and allowing the resulting sodium salt (18) to react with isoamyl nitrite] on treatment with hydriodic acid gave 2-amino-5-iodo-3-methyl- and 2-amino-5-iodo-... 

Normal nucleophilic substitution reactions of alkyl and aryl chloropyrazines have been examined as follows 2-chloro-3-methyl- and 3-chloro-2,5-dimethyl(and diethyl)pyrazine with ammonia and various amines (535, 679, 680) 2-chloro-3(and 6)-methylpyrazine with methylamine and dimethylamine (681, 844), piperidine and other amines (681, 921) 2-chloro-5(and 6)-methylpyrazine with aqueous ammonia (362) alkyl (and phenyl) chloropyrazines with ammonium hydroxide at 200° (887) 2-chloro-3-methylpyrazine with aniline and substituted anilines (929), and piperazine at 140° (759) 2-chloro-3-methyl(and ethyl)pyrazine with piperidine (aqueous potassium hydroxide at reflux) (930,931) [cf. the formation of the 2,6-isomer( ) (932)] 2-chloro-3,6-dimethylpyrazine with benzylamine at 184-250° (benzaldehyde and 2-amino-3,6-dimethylpyrazine were also produced) (921) 2-chloro-3,5,6-trimethylpyrazine with aqueous ammonia and copper powder at 140-150° (933) and with dimethylamine at 180° for 3 days (934,935) 2-chloro-6-trifluoromethylpyrazine with piperazine in acetonitrile at reflux (759) 2-chloro-3-phenylpyrazine with aqueous ammonia at 200° (535) 2-chloro-5-phenylpyrazine with liquid ammonia in an autoclave at 170° (377) 2-chloro-5-phenylpyrazine with piperazine in refluxing butanol (759) but the 6-isomer in acetonitrile (759) 5-chloro-2,3-diphenylpyrazine and piperidine at reflux (741) and 5-chloro-23-diphenylpyrazine with 2-hydroxyethylamine in a sealed tube at 125° for 40 hours (834). 

Dichloropyrazine in anhydrous ether with methyl magnesium iodide at 10° gave 2-chloro-6-methylpyrazine and 2,6-dimethylpyrazine and 2,3-dimethyl-pyrazine was likewise obtained from 2-chloro-3-methylpyrazine (687). A Grignard derivative has been prepared from 2-chloro-3,5,6-trimethylpyrazine and magnesium turnings in tetrahydrofuran and on treatment with diethyl sulfate produced 2-ethyI-3,5,6-trimethylpyrazine (330). 

Amino-5-bromomethyl-3-cyanopyrazine with the sodium salt of diethyl malonate in tetrahydrofuran at room temperature gave 2-amino-3-cyano-5-(2, 2 -diethoxycarbonylethyl)pyrazine together with a little dialkylated product (1031). Similar reactions were observed with the sodium salts of ethyl acetoacetate and ethyl 7-ethoxyacetoacetate, but methyl cyanoacetate gave only dialkylated product (1031). 2-Amino-5-chloromethyl-3-cyanopyrazine and 1-pyrroIidino-l-cyclohexene in tetrahydrofuran have been shown to give 2-amino-3-cyano-5-(2 -oxocyclohexyl-methyOpyrazine (542). 

Methylation of 2-hydroxy-3-7V-phenylcarbamoylpyrazine with dimethyl sulfate and potassium carbonate in boiling acetone gave l-methyl-2-oxo-3-A -phenylcarbamoyl-1,2-dihydropyrazine and the 3-(A -methyl-Af-phenylcarbamoyl) analogue was prepared likewise (1055). Similar methylation of 2-hydroxy-3-(o-methylaminophenyl)pyrazine produced 1 -methyl-3-(o-methylaminophenyl)-2-oxo-1,2-dihydropyrazine (1055). A series of 24iydroxy-3-(a-hydroxybenzyl)pyrazines has been methylated with dimethyl sulfate in aqueous sodium hydroxide to the 2-methoxy analogues (1045) and 2-benzyl-3,6-dihydroxy-5-methylpyrazine with diethyl sulfate and sodium ethoxide formed 2-benzyl-3,6-diethoxy-6-methylpyrazine (1066). 

The sodium salt of 2-hydroxypyrazine with thiophosphoryl chloride at room temperature gave 2-(dichlorophosphinothioyloxy)pyrazine (1112, 1113) and in N-methyl-2-pyrrolidone with ( ,6)-diethyl phosphorochloridothioate [(EtO)2P(=S)Clj it gave 2-(diethoxyphosphinothioyloxy)pyrazine (1114, 1115), also prepared in the absence of A(-methyl-2-pyrroIidone (1116). The potassium salt of 2-hydroxy-pyrazine in t-butanol-dioxane with 0,0-diphenyl phosphorochloridothioate... 

Amino-5-carboxypyrazine in anhydrous dimethylformamide with triethyl-amine and ethyl chloroformate and then diethyl glutamate and stirred at room temperature gave 2-amino-5-(l, 3 -diethoxycarbonylpropyl)carbamoylpyrazine (24) (1244). Similarly a mixture of 2-carboxypyrazine and triethylamine in methylene dichloride with ethyl chloroformate and morpholine gave 2-( -morpholinocarbonyl)-pyrazine (1351). 2-Carboxy-3-hydroxypyrazine refluxed with phosphorus tris(A-methylanilide) in toluene gave 2-hydroxy-3-(A-methyl-A-phenyIcarbamoyl)pyrazine (1055), and 2-hydroxy-3-(A -methyl-A -p-tolylcarbamoyl)pyrazine was prepared similarly (1055). Tetracarboxypyrazine heated with sulfur tetrafluoride (SF4) at 150° gave tetra(trifluoromethyl)pyrazine (899). 

A variety of methods exists for the synthesis of optically active amino acids, including asymmetric synthesis [85-93] and classic and enzymatic resolutions [94-97], However, most of these methods are not applicable to the preparation of a,a-disubstituted amino acids due to poor stereoselectivity and lower activity at the a-carbon. Attempts to resolve the racemic 2-amino-2-ethylhexanoic acid and its ester through classic resolution failed. Several approaches for the asymmetric synthesis of the amino acid were evaluated, including alkylation of 2-aminobutyric acid using a camphor-based chiral auxiliary and chiral phase-transfer catalyst. A process based on Schollkopf s asymmetric synthesis was developed (Scheme 12) [98]. Formation of piperazinone 24 through dimerization of methyl (5 )-(+)-2-aminobutyrate (25) was followed by enolization and methylation to give (35.6S)-2,5-dimethoxy-3,6-diethyl-3.6-dihydropyrazine (26) (Scheme 12). This dihydropyrazine intermediate is unstable in air and can be oxidized by oxygen to pyrazine 27, which has been isolated as a major impurity. 

After hydrogenation with Raney nickel at room temperature and 1 atmosphere pressure, an ethanolic suspension of diethyl 4-(acetonylamino)-3-nitropyridine-2,6-dicarbamate (8) cyclizes to afford diethyl 3-methyl-l,2-dihydropyrido[3,4-6]pyrazine-5,7-dicarbamate (9) in 65% yield.98... 

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