Imino Acids in the Murchison Meteorite: Evidence of Strecker Reactions

Introduction: Both α-amino acids and α-hydroxy acids occur in aqueous extracts of the Murchison carbonaceous meteorite. The Strecker-cyanohydrin reaction, the reaction of carbonyl compounds, cyanide, and ammonia to produce amino and hydroxy acids, has been proposed as a source of such organic acids in meteorites [1]. Such syntheses are consistent with the suggestion [2] that interstellar precursors of meteoritic organic compounds accreted on the meteorite parent body together with other ices [3]. Subsequent internal heating of the parent body melted these ices and led to the formation of larger compounds in synthetic reactions during aqueous alteration, which probably occurred at temperatures between 273K and 298K [4]. In the laboratory, imino acids are observed as important by-products of the Strecker synthesis (scheme-B). When R =CRXRYCO2H, C RXRYCONH2 or CRXRYCN, i.e., when NH2R is an amino acid, an amino acid amide, or an amino acid nitrile, imino acids are formed [5].