Guanine - Syntheses

Syntheses

Trace amounts of guanine form by the polymerization of ammonium cyanide (NH₄CN). Two experiments conducted by Levy et al. showed that heating 10 mol·L−1 NH₄CN at 80 °C for 24 hours gave a yield of 0.0007%, while using 0.1 mol·L−1 NH₄CN frozen at −20 °C for 25 years gave a 0.0035% yield. These results indicate guanine could arise in frozen regions of the primitive earth. In 1984, Yuasa reported a 0.00017% yield of guanine after the electrical discharge of NH₃, CH₄, C₂H₆, and 50 mL of water, followed by a subsequent acid hydrolysis. However, it is unknown whether the presence of guanine was not simply a resultant contaminant of the reaction.

10NH₃ + 2CH₄ + 4C₂H₆ + 2H₂O → 2C₅H₈N₅O (guanine) + 25H₂

A Fischer-Tropsch synthesis can also be used to form guanine, along with adenine, uracil, and thymine. Heating an equimolar gas mixture of CO, H₂, and NH₃ to 700 °C for 15 to 24 minutes, followed by quick cooling and then sustained reheating to 100 to 200 °C for 16 to 44 hours with an alumina catalyst, yielded guanine and uracil:

10CO + H₂ + 10NH₃ → 2C₅H₈N₅O (guanine) + 8H₂O

Another possible abiotic route was explored by quenching a 90% N₂–10%CO–H₂O gas mixture high-temperature plasma.

Traube's synthesis involves heating 2,4,5-triamino-1,6-dihydro-6-oxypyrimidine (as the sulfate) with formic acid for several hours.