Linked cycles of oxidative decarboxylation of glyoxylate as protometabolic analogs of the citric acid cycle.

The development of metabolic approaches towards understanding the origins of life, which have focused mainly on the citric acid (TCA) cycle, have languished-primarily due to a lack of experimentally demonstrable and sustainable cycle(s) of reactions. We show here the existence of a protometabolic analog of the TCA involving two linked cycles, which convert glyoxylate into CO2 and produce aspartic acid in the presence of ammonia. The reactions proceed from either pyruvate, oxaloacetate or malonate in the presence of glyoxylate as the carbon source and hydrogen peroxide as the oxidant under neutral aqueous conditions and at mild temperatures. The reaction pathway demonstrates turnover under controlled conditions. These results indicate that simpler versions of metabolic cycles could have emerged under potential prebiotic conditions, laying the foundation for the appearance of more sophisticated metabolic pathways once control by (polymeric) catalysts became available.

Anchimeric-Assisted Spontaneous Hydrolysis of Cyanohydrins Under Ambient Conditions: Implications for Cyanide-Initiated Selective Transformations.

Nitrile/cyanide hydrolysis is of importance from the perspective of organic chemistry, especially, prebiotic chemistry. Herein we report that cyanohydrins, generated by the reaction of cyanide with ß-keto acids and γ-keto-alcohols, spontaneously hydrolyze under ambient conditions (aqueous medium, RT, and a range of pH). The spontaneous hydrolysis is affected by an intramolecular proton transfer and an intramolecular 5-exo-dig attack, but with a twist. In the case of ß-keto acids, the hydrolysis is mediated by the neighboring carboxylic acid group only at pH values less than 7, whereas in the case of γ-keto-alcohols the hydrolysis is mediated by the neighboring hydroxyl group only at pH values greater than 7. The results, in combination with previous works, have implications for selective transformations of cyanide-initiated prebiotic systems chemistry.