Formation of Pentylpyridines in an Oil Medium.

The effects of an oil medium on the release of free ammonia from each of five amino acids (glycine, L-aspartic acid, L-asparagine, L-glutamic acid, L-glutamine) and the formation of pentylpyridines were studied. Among the five amino acids, only asparagine and glutamine generated ammonia readily by deamidation of amide side chains at 180 degrees C under oil conditions, even though both of them produced less ammonia than under aqueous conditions. However, the difference in the relative amounts of ammonia released between asparagine and glutamine was larger under oil conditions and much more free ammonia was liberated from glutamine than from asparagine. On the other hand, when each of the five amino acids was reacted with 2,4-decadienal under oil conditions, an increased amount of 2-pentylpyridine could be produced from asparagine and glutamine compared to aqueous conditions. Specifically, >10 times the amount of 2-pentylpyridine was found in the reaction of glutamine and 2,4-decadienal under oil conditions than under aqueous conditions despite the fact that both asparagine and glutamine could liberate less ammonia in oil systems. However, only a small amount of 3-pentylpyridine was formed in the asparagine and glutamine that produced a large amount of 2-pentylpyridine under oil conditions.