A Prebiotic Surface Catalysed Photochemically Activated Synthesis of a-Lipoic Acid

Abstract: Catalysts such as Mg.porphin may coordinate alkynes such as ethyne and catalyse their photchemically activated oligomerization. The multicentre catalyst may also form a charge transfer adduct with anions such as hydrogen disulphide anion centred on its magnesium ion. Both adducts may exhibit net negative charges which determine their orientations when subject to the magnetic field of exciting radiation. The preferred orientation determines the asymmetry of the adducts when they bond to form a complex. The negatively charged complex may then loose hydrogen anion to become neutral. Subsequent reaction with hydroxyl radicals to form a 1,1’-dihydroxy complex allows enolisation to form the carboxylic acid. Further hydrogenation and activation allows the separation of the a-lipoic acid from the catalyst. The reactions have been shown to be feasible from the overall enthalpy changes in the ZKE approximation at the HF and MP2 /6-31G* level.