Phenylalanine and tyrosine synthesis under primitive earth conditions.

Phenylacetylene can be synthesized in substantial yields from various hydrocarbons by high temperatures, electric discharges, and ultraviolet light. Phenylacetylene is hydrated to phenylacetaldehyde by way of both nucleophilic and radical additions of H2S followed by hydrolysis of the thtioaldehyde. The addition of NH3 and HCN to phenylacetaldehyde yields phenylalanine nitrile which is hydrolyzed to phenylalanine. A small yield of tyrosine is obtained from the radical addition of H2S to phenylacetylene. This sequence of reactions is a possible mechanism for the synthesis of these amino acids on the primitive earth.