Amino acids of the Murchison meteorite: II. Five carbon acyclic primary beta-, gamma-, and delta-amino alkanoic acids.

All ten of the possible five-carbon acyclic primary beta-, gamma-, and delta-amino alkanoic acids (amino position isomers of the valines) have been positively identified in hot-water extracts of the Murchison meteorite using combined gas chromatography-mass spectrometry (GC-MS) and ion exchange chromatography. With the exception of delta-aminovaleric acid, none of these amino acids has been previously reported to occur in meteorites or in any other natural material. The gamma-amino acids (4-aminopentanoic acid, 4-amino-2-methlybutanoic acid, and 4-amino-3-methylbutanoic acid) are present at higher concentrations (about 5 nmol g-1)than are the beta-amino isomers (3-aminopentanoic acid, 3-amino-2-methylbutanoic acid, allo-3-amino-2-methylbutanoic acid, 3-amino-3-methylbutanoic acid, 3-amino-2-ethylpropanoic acid, and 3-amino-2,2-dimethylpropanoic acid) which are present at concentrations of 1-2 nmol g-1. These amino acids are less abundant in the meteorite than either the corresponding alpha-amino acids or the four-carbon homologues. Thirty-six amino acids have now been positively identified in the Murchison meteorite, 17 of which are apparently unique to carbonaceous chondrites. The fact that the meteorite contains all possible five-carbon acyclic primary alpha-, beta-, gamma-, and delta-amino alkanoic acids is consistent with a synthetic process involving random combination of single-carbon precursors.