Strecker proline

Proline and hydroxyproline differ from the other amino acids in that they contain a secondary amino group in a pyrrolidine ring therefore, they do not produce aminoketones and Strecker aldehydes in the reaction with dicarbonyls, ffowever, nitrogen heterocyclics are produced, including 1-pyrroline, pyrrolidine, 2-acetyl-1-pyrroline and 2-acetyltetrahydropyridine (Scheme 12.5) [19]. 

Proline Pyrrolidine, 1-pyrroline. No Strecker aldehyde Important intermediates for bread-like aromas... 

Heating of dihydroxyacetone in the presence of phosphate ions in known to produce substantial amounts of pyruvaldehyde (10). Furthermore pyruvaldehyde is assumed to catalyze the formation of 1-pyrro-line by Strecker degradation of proline (11). To study the role of 1-pyrroline and pyruvaldehyde in Acp formation, three additional experiments were conducted. 

Das aus Pyrrolidin durch N-Chloricrung und anschlieBende Chlorwasserstoff-Abspal-tung mit Basen zugangliche 3,4-Dihydro-2H-pyrrol addiert in Analogie zur Strecker-Reak-tion mit Iminen (s. S. 535) Cyanwasserstoff zum 2-Cyan-pyrrolidin. Durch saure Hydrolyse wird dl-Prolin erhalten (Gesamtausbeute 45%)7 ... 

Scheme 3.33 Strecker reactions catalysed by L-proline-derived A,A -dioxide.

Hodge et al. [49] originally proposed a mechanism for the formation of pyrroles, which is also supported by Tressl et al. [50]. This basically is the participation of proline and hydroxy proline in the Strecker degradation to yield pyrroles. If the food system does not contain either proline or hydroxy proline, then a sugar of at least five or more carbons is required for pyrrole formation [51]. 

Strecker degradation of both proline (cf. Formula 5.14) and ornithine (cf. Formula 5.15). 

The Strecker degradation of ornithine proceeds analogously, but the intermediate 4-aminobutanal forms by cychsation the final product, 1-pyrroHne (Figure 2.59). This reaction is important for the development of the characteristic aroma of bread crust (see Section 8.2.12.4.1), the aroma of other cereal products, certain fragrant rice varieties (such as Basmati rice) and in the biosynthesis of pyrrolidine alkaloids in plants (see Section 10.3.2.1.1). It was proposed that pyrrolidine and l-pyrrohne also result upon Strecker-type reaction of proline by a-dicarbonyl compounds. 

Smith, A.D., M. Benziman, andH.J. Strecker, 1967. The formation of ornithine from proline in animal tissues. Biochem. J. 104, 557-563. 

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