Chemoenzymatic synthesis of aroma active 5,6-dihydro- and tetrahydropyrazines from aliphatic acyloins produced by baker's yeast |
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Authors: | Kurniadi Toshinari Bel Rhlid Rachid Fay Laurent-Bernard Juillerat Marcel-Alexandre Berger Ralf Günter |
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Institution: | Nestlé Research Center, Vers-chez-les-Blanc, P.O. Box 44, 1000 Lausanne 26, Switzerland. |
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Abstract: | Twenty-five acyloins were generated by biotransformation of aliphatic aldehydes and 2-ketocarboxylic acids using whole cells of baker's yeast as catalyst. Six of these acyloins were synthesized and tentatively characterized for the first time. Subsequent chemical reaction with 1,2-propanediamine under mild conditions resulted in the formation of thirteen 5,6-dihydropyrazines and six tetrahydropyrazines. Their odor qualities were evaluated, and their odor thresholds were estimated. Among these pyrazine derivatives, 2-ethyl-3,5-dimethyl-5,6-dihydropyrazine (roasted, nutty, 0.002 ng/L air), 2,3-diethyl-5-methyl-5,6-dihydropyrazine (roasted, 0.004 ng/L air), and 2-ethyl-3,5-dimethyltetrahydropyrazine (bread crustlike, 1.9 ng/L air) were the most intensive-smelling aroma active compounds. |
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