Iminodicarboxylic acids in the Murchison meteorite: Evidence of Strecker reactions

Abstract

α-Amino acids and α-hydroxy acids are well known constituents of several carbonaceous meteorites. One proposed mechanism of their formation is the reactions of CN −, NH 3, aldehydes and ketones in aqueous solution, a Strecker-like synthesis. Iminodicarboxylic acids, relatively unusual in molecular structure, are significant by-products of laboratory Strecker syntheses of α-amino acids. It is therefore notable that an analogous suite of imino acids has not been reported in CM2 chondrites where amino and hydroxy acids are abundant. In this work, aqueous extracts of the Murchison meteorite were examined for the presence of imino acids; GC-MS and HPLC molecular analyses revealed a complex suite of such acids. With the exception of one of the seven-carbon members, all of the C4 through C7 imino acids were observed in Murchison. These observations suggest that the Strecker synthesis made, at least, some contribution to the formation of extraterrestrial amino acids.