A Computational Study of a Prebiotic Synthesis of Menaquinone, Phylloquinone, and Vitamin K Analoges

Abstract

Ab initio applied computing is used to determine the viability of a plausible mechanism for the formation of vitamin K from planetary and interstellar gases that contain the necessary essential elements in prebiotic chemistry before the advent of life on Earth. The immutable laws of chemical thermodynamics and kinetics enable the intermediates in the synthesis to be characterized and the activation energies to be established. The planetary molecules propyne, ethyne, carbon monoxide, hydrogen, and water are invoked in a synthesis of menaquinone, a naphthoquinone precursor of the vitamin K series of molecules. The enthalpy change was -0.43 h. This is followed by the formation of oligomers of the gases propyne and ethyne which serve as side-chains for the analogs of vitamin K where the enthalpy change was -0.21 h for the 2-methyl butane side-chain. For vitamin K (n=1), the total enthalpy change was -0.63 h. The additional presence of hydrogen cyanide gas and magnesium ions enables the surface-catalyzed, photochemically activated synthesis of the catalyst, magnesium metalloporphyrin. The activation energies for the formation of intermediates on the surface of the catalyst are less than the first excitation energy, 0.21 h. Finally, the menaquinone derivative and the 2-methyl butane or 2-methyl butene oligomer derivatives are combined to give specific analogs of vitamin K. The reactions are feasible from the overall enthalpy changes in the ZKE approximation at the HF and MP2 /6-31G* level and with acceptable activation energies.