title: Sugar-driven prebiotic synthesis of 3,5(6)-dimethylpyrazin-2-one: a possible nucleobase of a primitive replication process.
abstract: Reaction of glyceraldehyde with alanine amide (or ammonia) under anaerobic aqueous conditions yielded 3,5(6)-dimethylpyrazin-2-one that is considered a possible complementary residue of a primitive replicating molecule that preceded RNA. Synthesis of the dimethylpyrazin-2-one isomers under mild aqueous conditions (65 degrees C, pH 5.5) from 100 mM glyceraldehyde and alanine amide (or ammonia) was complete in about 5 days. This synthesis using 25 mM glyceraldehyde and alanine amide gave a total pyrazinone yield of 9.3% consisting of 42% of the 3,5-dimethylprazin-2-one isomer and 58% of the 3,6-dimethylpyrazin-2-one isomer. The related synthesis of the dimethylpyrazin-2-one isomers from glyceraldehyde and ammonia was about 200-fold less efficient than the alanine amide reaction. This synthetic process is considered a reasonable model of origin-of-life chemistry because it uses plausible prebiotic substrates, and resembles modern biosynthesis by employing the energized carbon groups of sugars to drive the synthesis of small organic molecules. Possible sugar-driven pathways for the prebiotic synthesis of polymerizable 2-pyrazinone monomers are discussed.
authors.affiliation: SETI Institute, NASA Ames Research Center, Mail Stop 239-4, Moffett Field, CA 94035-1000, USA. Arthur.L.Weber@nasa.gov
authors.forename: Arthur L
authors.initials: AL
authors.lastname: Weber
mesh_terms: D000409:Alanine / Q000737:chemistry*; D000577:Amides; D000588:Amines / Q000737:chemistry; D000643:Ammonium Chloride / Q000737:chemistry; D001482:Base Composition; D002241:Carbohydrates / Q000737:chemistry*; D002621:Chemistry / Q000379:methods*; D019418:Evolution, Chemical; D005985:Glyceraldehyde / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D008956:Models, Chemical; D000069497:Origin of Life; D011719:Pyrazines / Q000737:chemistry* / Q000378:metabolism; D013056:Spectrophotometry, Ultraviolet; D013997:Time Factors
chemical_list: C531985:3,5(6)-dimethylpyrazin-2-one; D000577:Amides; D000588:Amines; D002241:Carbohydrates; D011719:Pyrazines; D000643:Ammonium Chloride; D005985:Glyceraldehyde; D000409:Alanine