- Flavor Contribution and Formation of the Intense Roast-Smelling Odorants 2-Propionyl-1-pyrroline and 2-Propionyltetrahydropyridine in Maillard-Type Reactions
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Application of aroma extract dilution analysis on two different model mixtures of proline and glucose, reacted under aqueous or dry-heating conditions, revealed 2-propionyl-1-pyrroline (PP) and 2-propionyltetrahydropyridine (PTHP; occurring in two tautomers), besides 2-acetyl-1-pyrroline and 2-acetyltetrahydropyridine, as important roast-smelling odorants in both mixtures. A comparison of the isotope distribution in PP and PTHP formed from either 13C6-labeled or unlabeled glucose suggested a formation pathway for both odorants from the same intermediate, 1-pyrroline, when reacted with either 2-oxobutanal (yielding PP) or 1-hydroxy-2-butanone (yielding PTHP). 2-Oxobutanal, a possible precursor of 1-hydroxy-2-butanone, was shown to be formed in high yields (29 mol %) by reacting acetaldehyde and glycolaldehyde, two well-known degradation products of carbohydrates.
- Hofmann, Thomas,Schieberle, Peter
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- A general method for the synthesis of the most powerful naturally?occurring Maillard flavors
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The natural flavors 2-acetyl-1-pyrroline 1a, 2-propionyl-1-pyrroline 1b, 2-acetyl-3,4,5,6-tetrahydropyridine 1c, 2-acetyl-2-thiazoline 1d, 2-propionyl-2-thiazoline 1e, and the artificial flavor 2-acetyl-5,6-dihydro-4H-1,3-thiazine 1f have been prepared by catalytic SeO2 oxidation of the corresponding cyclic imines 6a-c and sulfur cyclic imines 7a-c using TBHP as co-oxidant. The oxidation of the pyrrolines 1a and b is completely regioselective. Professional olfactory evaluation together with the odor threshold of the new flavor 1f is reported.
- Fuganti, Claudio,Gatti, Francesco G.,Serra, Stefano
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- Method for synthesizing 2-propionyl-1-pyrroline
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The invention belongs to the technical field of chemical synthesis, in particular to a method for synthesizing 2-propionyl-1-pyrroline, comprising the steps of: 1) dissolving pyrrolidine-2-one in dichloromethane, adding dimethylaminopyridine and triethylamine, adding di-tert-butyl dicarbonate under stirring, and after the reaction is finished, conducting washing with distilled water and saturatedbrine; 2) dissolving the intermediate product obtained in the above step in tetrahydrofuran, dropwise adding tetramethylethylenediamine and a Grignard reagent in a low temperature environment to obtain N-boc-4-oxo-aminoheptane; 3) reacting the N-boc-4-oxo-aminoheptane with trifluoroacetic acid to remove the Boc group to obtain propylpyrroline; and 4) conducting specific oxidation on the propylpyrroline by selenium dioxide to obtain a final product 2-propionyl-1-pyrroline. The method has the advantages of simple operation, low cost, low energy consumption, high yield, high product purity and the like, and is more suitable for industrial production.
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Paragraph 0017; 0020
(2019/04/26)
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- Penicillin acylase-mediated synthesis of 2-acetyl-1-pyrroline and of 2-propionyl-1-pyrroline, key roast-smelling odorants in food. Inclusion complexes with i-cyclodextrin and their NMR and MS characterization
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The synthesis of the strong natural roast odorants 1 and 2 is achieved from the C-6 isomeric alcohols 16 and 21 via the acetylenic C-6 and C-7 amines 8 and 9. Key step in the process is the hydrolysis of the W-phenylacetamides 12 and 13 by means of immobilized penicillin acylase, which affords the l-amino-4,5-diketones 14 and 15, spontaneously ring closing to 1 and 2. These latter compounds form inclusion complexes with/?-cyclodextrin, as demonstrated by NMR measurements in deuterated water and FAB-MS spectra.
- Favino, Tito Fabrizio,Fronza, Giovanni,Fuganti, Claudio,Fuganti, Daniela,Grasselli, Piero,Mele, Andrea
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p. 8975 - 8979
(2007/10/03)
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- Synthesis of 2-Acetyl-1-pyrroline, the Principal Rice Flavor Component
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A new straightforward synthesis of 2-acetyl-1-pyrroline, the principal rice flavor component with a cracker-like flavor, is reported.The reaction sequence involves the conversion of pyrrolidine into tripyrroline, subsequent hydrocyanation of the latter into 2-cyanopyrrolidine, oxidation into 2-cyano-1-pyrroline, and Grignard addition of methylmagnesium iodide, affording an overall yield of 16-19percent from pyrrolidine.In similar way, 2-propionyl-1-pyrroline, a recently discovered flavor component of popcorn, was prepared in addition to several higher analogues, i.e., 2-acyl-1-pyrrolines.Also, the synthesis of 2-(acetyl-d3)-1-pyrroline, a deuterated derivative of the rice flavor compound which is useful for the stable isotope dilution assay, is described.
- Kimpe, Norbert G. De,Stevens, Christian V.,Keppens, Marian A.
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p. 1458 - 1461
(2007/10/02)
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