A Prebiotic Surface Catalysed Photochemically Activated Synthesis of L-Cysteine

摘要

Ethyne forms a weak charge-transfer complex with surface catalysts such as Mg.porphin in which the ethyne group has a net positive charge (0.08), and the conjugated porphin has a negative charge. This neutral complex is polarised and undergoes a nucleophilic addition reaction with ammonia at the carbene carbon to form Mg.2-amino ethenyl.porphin which has a tendency to the formation of cyclic Mg.1H aziridin-2yl.porphin complex. Nucleophilic attack by hydrosulfide anion ultimately yields a complex of bound 2-mercapto ethanimine. When the imine is bound to a Mg.porphin complex in which carbon monoxide has been oriented by exciting radiation an aziridine-2one complex is formed hydrolysable to the amino acid L-cysteine. 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.