2-Amino-3-bromo-6-chloropyrazine CAS 212779-21-0

Pyrazines can be categorized based on their substituents, with common types including: alkylpyrazines (like 2-methylpyrazine, 2-ethylpyrazine, 2,3-dimethylpyrazine), alkoxy-pyrazines (like methoxypyrazine, ethoxypyrazine), acylpyrazines (like acetylpyrazine), and poly-substituted pyrazines with various combinations of alkyl groups on the pyrazine ring; these are often found in food products like coffee, roasted nuts, and baked goods, contributing to their characteristic aroma and flavor.

Key examples of pyrazine types:
Simple alkylpyrazines:
2-Methylpyrazine
2-Ethylpyrazine
2,3-Dimethylpyrazine
2,5-Dimethylpyrazine

L-rhamnose with and without leucine
Initially, 1.64 g of L-rhamnose, 5 mL of NH4OH and 4.5 mL of H2O were reacted with and without leucine (0.4 g) at 110°C for 2 hours. All pyrazines were eluted from the column within 5–15 min, and the related chromatograms were representative of the profiles for the pyrazines obtained from all of the reactions and sample preparations. It is important to note that the DCM extract of the reaction containing leucine showed the presence of more branched pyrazines such as 2-isoamyl-6-methylpyrazine, with an elution time of 9.54 min compared to the DCM extract of a similar reaction without leucine. Also, the DCM extract of both reaction products showed the presence of the undesirable 4-methyl imidazole with an elution time of 13.95 min.

HFCS + leucine
Approximately 3 g of HFCS were mixed with 0.8 g of L-leucine, 10–12 mL of NH4OH and 8–10 mL of H2O. The mixture was heated for 2 hours at 110°C. After the reaction was completed, 5 g of sodium chloride were dissolved in the mixture, which was extracted 4 times with 25–35 mL of hexane. After repeated hexane extractions, the mixture was extracted for the fifth time with 90/10 hexane/DCM and finally with only DCM. With each hexane extraction, the concentration of pyrazines appeared to decrease. In this regard, most of the relatively high alkyl substituted branched pyrazines were extracted during the first and second hexane extractions. Use of a 90/10 hexane/DCM extract of the same reaction products produced an extract with additional pyrazines as well as undesirable 4-methylimidazole (tR = 13.94 min). An analysis of the final 100% DCM extract of the same reaction product revealed no pyrazines. It is important to note that a relatively large peak, which eluted with tR = 12.89 min, could be assigned to 5-methyl-2-pyrazinylmethanol.

CDS with and without leucine
A total of 10 g of CDS, an aqueous solution containing 25% fructose, 45% glucose and 0.65% sucrose, obtained from R.J. Reynolds Tobacco Company, were mixed with 20 mL of NH4OH and 10 mL of H2O. The mixture was heated at 110°C for 2 hours. The reaction mixture was cooled after which 5 g of NaCl was dissolved, followed by extraction six times with fresh pure hexane, wherein the quantity of pyrazines decreased, as found above. Branched pyrazines, like the isoamyl derivative described above, were not detected since no amino acid was used. The last extraction was performed using 100% DCM, which revealed additional pyrazines.

The same reaction was repeated with the presence of 1 g of leucine. After the reaction was terminated, 5 g of NaCl were added and extracted 5 times, first with 25 mL of fresh hexane and then 100% DCM. Qualitative and relative quantitative results regarding the pyrazines produced by this reaction were very similar to those described in reaction 2 above. Based upon the above experiments, the repetitive extractions (~6) will be required for removal of all pyrazines.