Biochemical compounds, prebiotic

It is now quite clear that HCN-aqueous ammonia reaction mixtures have a prominent role in the prebiotic synthesis of biochemical compounds. In addition to a variety of... 

Following Miller s experiment, many chemists successfully synthesized other compounds of biochemical relevance under prebiotic conditions - thereby demonstrating convincingly that several molecular bricks of life might have been present on prebiotic Earth. 

For several decades, Oparin s model remained uncontradicted, the more so because experiments simulating prebiotic atmospheric conditions and applying electric discharges, ionizing particles, or UV-radiation were able to synthesize amino acids, small peptides, sugars, heterocyclic compounds and other biochemical molecules. 

Fortunately, my graduate research in biochemistry at Baylor College of Medicine, in Houston, involved studies on the mechanism of formic acid oxidation in animal tissues and on the incorporation of this one-carbon compound into nucleic acid components and their precursors. This provided me with experience in the use of isotopic tracers and the background in biochemical research which proved crucial, in later years, for unraveUng the intermediates and mechanisms of synthesis of purines and other compounds, when I discovered the prebiotic synthesis of adenine and other building blocks of nucleic acids, and a general pathway or method for the prebiotic formation of oligodeoxynucleotides and peptides. 

The prebiotic synthesis of adenine was confirmed by C. U. Lowe, M. W. Rees and R. Markham, and indirectly by Ponnamperuma and co-workers. The former authors also found the fourth common biological purine, hypoxanthine, in the reaction product from HCN and ammonia mixtures. It may be noted that the above sequence of reactions follows the same direction (first imidazole, then pyrimidine eyclization) as the biochemical synthesis of purines. The kinetics and mechanisms of HCN oligomerization as well as the potential role of the HCN trimer and tetramer for purine synthesis were studied by several investigators, particularly by J. P. Ferris and L. Orgel and coworkers. The yields of purines from HCN are quite low but after isolating the appropriate intermediates, e.g. aminomalonodinitrile (AMN), diaminomaleodinitrile (DAMDN), AICN, AICAI, AICA, and condensing them with formamidine or other one-carbon compounds, substantial yields of adenine and the other purines can be obtained. 

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