New insights into the synthesis and characterization of 2-methoxy-3-alkylpyrazines and their deuterated isotopologues

作者：Schmarr H G^*; Sang W; Ganss S; Koschinski S; Meusinger R

来源：Journal of Labelled Compounds and Radiopharmaceuticals, 2011, 54(8): 438-440.

DOI：10.1002/jlcr.1888

• methoxypyrazines
• synthesis
• characterization
• NMR
• GC-MS
• linear retention indices

A previously described synthetic route for preparation of 2-methoxy-3-alkylprazines (MPs) based on condensation of glyoxal with an a-amino acid amide, followed by methylation with iodomethane yields 3-alkyl-1-methyl-1H-pyrazin-2-ones (N-methyl derivatives), rather than the designated 2-methoxy-3-alkylpyrazines (O-methyl derivatives). Despite similar nuclear magnetic resonance and mass spectral properties, gas chromatographic (GC) retention indices differ significantly, indicating chemical difference. With the example of 3-sec-butyl-1-methyl-1H-pyrazin-2-one and its 3-sec-butyl-1-[(2)H(3)]methyl-1H-pyrazin-2-one isotopologue, the position of the methyl group introduced could be assigned unambiguously, using heteronuclear multiple bond correlation (HMBC) NMR experiments. For future characterization, the spectroscopic (NMR, EI(+) MS) as well as GC retention index data on two stationary phases of the most aroma relevant MPs and their deuterated isotopologues are summarized.

• 出版日期2011-6