Synthesis of Purine

Purines

Purines are cyclic diureides with the skeleton of purine which consists of a pyrimidine ring fused with an imidazole ring. Purine and its derivatives exists in two tautomeric forms as given below-

Purine is a colorless solid with melting point 216°C. It is highly soluble in water. It shows both acidic and basic properties.
Purine is of two types i.e. Oxypurines and Aminopurines.
Oxipurines are hydroxy derivatives of purine (e.g. Uric acid, Xanthine etc.) and they can exhibit keto-enol tautomerism.
Aminopurines are amino derivatives of purine which is found in each and every living cell in the form of nucleic acids. e.g. Adenine, Guanine etc.

Synthesis of Purine from Uric Acid

Uric acid converted into 2,6,8-trichloropurine with POCl₃ which reacts with HI at 0°C gives 2,6-diiodopurine. 2,6-diiodopurine is reduced to purine with Zn-dust.

Synthesis of Purine from Formic Acid and 4,5-diaminopyrimidine

Isolation of Uric Acid From Human Urine

Uric acid may be isolated from human urine by concentrating it with concentrated HCl. The crystal of uric acid is separate out on cooling.

Isolation of Uric Acid From From Guano

Uric acid may be prepared on large scale from the excrement of birds or snakes(Guano). The dry powdered excrement is boiled with conc. caustic soda solution at 80-100° C for about seven hours. The product is filtered and collected in a vessel having HCl where the uric acid is crystallised out on colling. Now it is purified by dissolving in 5% caustic soda solution. The solution is concentrated and then cooled to get sodium urate crystal which are redissolved in dilute caustic soda and finally precipitated with HCl.

Structure Determination of Uric Acid

Synthesis of Uric Acid