2- Methoxy-3- pyrazine

Comparison of the ortho and para indirect deactivation in 155 and 156 with that in 151 and 152 would reveal the relative effectiveness of the two effects and the influence of the ring-position. Additional examples of deactivation are ortho indirect in 2-chloro-6-methoxy-pyrazine ortho direct in 4-chloro-5-methoxypyrimidine para direct in 2-chloro-5-methoxypyrimidine ortho and para indirect in the... 

Sulfanilamido-3-Methoxy-Pyrazine 1.5 grams of the product from the preceding step... 

Closely related compounds, even enantiomers, may not show similar binding affinities. OBP1 specifically bound 2- H-3 -isobutyl-3-methoxypyrazine, whereas OBP2 did not a derivative compound (2-isobutyl-3-methoxy-pyrazine) was unable to displace ligands from OBP-2 (Lobel et al., 1998). 

Geosmin, 2-Methyl isobomeol (MIB) and 2-isopropyl methoxy pyrazine are known to be produced by various types of actinomycete cultures (10-15). Geosmin and MIB are saturated tertiary alcohols and resist oxidation. The steric configuration of the hydroxyl and methyl groups in both compounds are believed to interact with receptors in the nose, imparting their characteristic earthy odour (16). The four compounds itemised as the key osmogenes in this odorous emission have extremely low odour threshold concentrations. Their occasional occurence in drinking water can lead to widespread complaints and are routinely monitored for within this Authority. 

Alkyl-2-methoxypyrazines exhibit a base peak at miz 124 in the mass spectrum. The peak corresponds to a molecular ion in 2-methoxy-3-methylpyrazine (24a) and to a fragment ion, resulting from a McLafferty rearrangement of an alkyl group, in 3-isopropyl-2-methoxypyrazine (24b) and 3-5cc-butyl-2-methoxy pyrazine (24d) (97). 

Methoxypyrazines 3-isobutyl-2-methoxy-pyrazine, 3-isopropyl-2-methoxypyrazine Strong X No ... 

Perfluoropyrazine (17) on reaction with sodium methoxide gives 2,3,5-trifluoro-6-methoxy-pyrazine and 2,3-difluoro-5,6-dimethoxypyrazine.130... 

Ethyl-3-methoxypyrazine (3-Ethyl-2-methoxy pyrazine) C2H5 och3... 

Isopropyl-2-methoxy pyrazine (2- Isopropy 1 - 3- methoxy pyrazine) och3 i i-C3H7... 

Isopropyl-5-methoxy pyrazine (5-Isopropyl-2-methoxypyrazine) i-C3H7 OCH3... 

Isobutyl-3-methoxy pyrazine (3-Isobutyl-2-methoxy pyrazine) i-c4H9 och3... 

The desirable concentration for the aroma is small, 8.15 ng/L levels of 30 ng/L are perceived as unharmonic (69JAFC1322,03MI8). The methoxy-pyrazines form in the grapes from glycine, leucine, isoleucine, and valine via diketopiperazine intermediates. After enolization, O-methylation, and dehydration the pyrazines are formed (01MI329,10MI77,11JAFC7310). 

Amino-3-Methoxy-Pyrazine 3 grams of 2-amino-3-methoxy-5-bromo-pyrazine are hydrogenated, in methanolic solution at room temperature and at atmospheric pressure, in the presence of 1 gram of palladium over charcoal... 

Sulfanilamido-3-Methoxy-Pyrazine 1.5 grams of the product from the preceding step and 7 to 8 ml of aqueous 10% sodium hydroxide are boiled for 1 hour. The cooled solution is slightly acidified to pH 6 with aqueous 2 N hydrochloric acid and the product is filtered. The yield is 1.25 grams, melting at 175°C. 

Geosmin, 2-isopropyl, 3-methyox pyrazine, 2-isobutyl-3-methoxy-pyrazine, 2-methyl isobomeol, 2,3, 6 trichloroanisole ... 

Methyl 6-benzyloxy-5-isobutyl-3-methoxy-2-pyrazinecarboxylate 4-oxide (121, R = C02Me) gave 2-benzyloxy-6-hydroxymethyl-3-isobutyl-5-methoxy-pyrazine 4-oxide (121, R = CH2OH) [LiAl(OBu03H, THF, 0 7°C, 18 h ... 

Methoxy-3,6-dimethylpyrazine 4-oxide (283) gave only 2-acetoxymethyl-3-methoxy-5-methylpyrazine (284) (neat AC2O, reflux, 1 h 88%) 324 in contrast, the homologous substrate, 2,5-dibenzyl-3-methoxypyrazine 1-oxide (285), gave a separable mixture of 2-(a-acetoxybenzyl)-5-benzyl-3-methoxy-pyrazine (286) and 2-acetoxy-3,6-dibenzyl-5-methoxypyrazine (287) (neat Ac20, reflux, 90 min 55 and 20%, respectively).312... 

Although most of the alkylpyrazines are formed through thermal Interactions of components in food, methoxy-substltuted pyrazlnes are mainly derived from biosynthetic pathways. 2-Isobutyl-3-methoxy-pyrazine Isolated from bell pepper by Buttery at al. (14) is one of the most significant flavor compounds discovered. This characteristic bell pepper aroma compound has an extremely low odor threshold of 0.002 ppb in water (15). 

Ring aUylation and propenylation of methylpyrazine has been described (634) acetonylpyrazine with phenyllithium gives 2-acetonyl-6-phenylpyrazine (639) and 2,5-dimethylpyrazine with isopentylUthium gave 3-isopentyl-2,S-dimethylpyrazine (70). Aldehydes and ketones in the presence of a solution of an alkali or alkaline earth metal in liquid ammonia, or a suspension of these metals in other solvents, can be used to alkylate the pyrazine ring in moderate to good yields (614, 640, 641). This alkylation has been successfully applied to alkyl- and dialkyl(amino- and methoxy)pyrazines, and a mechanism has been proposed for the reaction (614). For example, the reaction of potassium with methylpyrazine and ethyl methyl ketone, catalyzed by sodamide (0.25 mol) gave 88% of 2 -butyl-6-methylpyrazine. 

A three-dimensional X-ray structure determination of 2,5-dichloro-3-methoxy-pyrazine (915) and 2,3-dichloro-5-ethyIamino-6-methoxypyrazine (916) has been completed. 

The methylsulfonyl substituent was readily displaced from pyrazine. Thus 2-methylsulfonylpyrazine (7) with methoxide ion at 87° for 3 hours gave 2-methoxy-pyrazine (1079), and 2-methylsulfinylpyrazine displayed similar reactivity, but 2-methylthiopyrazine was less reactive (1080). 

Methylation of 2-amino-3-hydroxypyrazine (62) with methyl iodide and sodium methoxide afforded 3-amino-l-methyl-2-oxo-1,2-dihydropyrazine (63), and when an excess of methyl iodide was used, a mixture of compound (63) and its methio-dide (64) was isolated. Reaction with dimethyl sulfate and alkaU gave compound (63) and l,4-dimethyl-2,3-dioxo-l,2,3,4-tetrahydropyrazine (66) the latter was presumed to be formed by hydrolysis of an intermediate quaternary salt since it was also obtained by treatment of the methiodide (64) with aqueous sodium hydroxide. Reaction of 2-amino-3-hydroxypyrazine with ethereal diazomethane produced a mixture of N- and 0-methyl derivatives, (63) and 2-amino-3-methoxy-pyrazine (65). With methyl toluene-p-sulfonate the quaternary salt 2-amino-3-hydroxy-1-methylpyrazinium toluenesulfonate (67) was obtained on alkaline hydrolysis it gave 3-hydroxy-l-methyl-2-oxo-l,2-dihydropyrazine (68) (832). Pulcherriminic acid with diazomethane gave a dimethyl derivative (99). 

Oxidation of 2-isobutyl-3-methoxy-5-(2 -methylprop-l -enyl)pyrazine (95) with peroxymaleic acid gave 5-(r,2 -epoxy-2 -methyl)propyl-2-isobutyl-3-methoxy-pyrazine 1-oxide (27) (113b). 

Chlorocarbonyl-2-methoxy-5-methylpyrazine with lithium dimethyl copper reagent in ether gave 3-acetyl-2-methoxy-5-methylpyrazine 2-acetyl-3-methoxy-pyrazine and 2-acetyl-3,6-dimethoxy-5-methylpyrazine were prepared similarly (844), but 2-chlorocarbonyl-3-methoxy-5-methylpyrazine with lithium dimethyl copper in ether gave a mixture of 2-acetyl-3-methoxy-5-methylpyrazine and 2-(l-hydroxy-1-methylethyl)-3-methoxy-5-methylpyrazine (844). 

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