PURINE AND PYRIMIDINE

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PURINES AND PYRIMIDINES: 

PURINES AND PYRIMIDINES

HISTORY : 

HISTORY In 1868 Frederich Miescher isolated nucleic acid (then called nuclein ) from pus cells. Albrecht kossel differentiated RNA and DNA in 1882. Altmann introduced the term nucleic acid in 1889. In 1906, kossel described the 4 bases in nucleic acid.

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In order to understand the structure and properties of DNA and RNA, we need to look at their structural components. Nucleotides are the building blocks of nucleic acids Building blocks of nucleic acids (RNA, DNA) We begin with certain heterocyclic aromatic compounds called pyrimidines and purines .

Purines and Pyrimidines: 

Purines and Pyrimidines Purine and Pyrimidine are the names of the parent compounds of two types of nitrogen-containing heterocyclic aromatic compounds. N N N N N N H Pyrimidine Purine

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A purine is a heterocyclic aromatic organic compound , consisting of a pyrimidine ring fused to an imidazole ring. Purines , including substituted purines and their tautomers , are the most widely distributed kind of nitrogen-containing heterocycle in nature. Purines consist of a six- membered and a five- membered nitrogen-containing ring, fused together. The purine bases have a 9-membered double-ring system with four nitrogens and five carbons. Adenine and guanine are the principal purines of both DNA and RNA. Adenine (6-Aminopurine ) Gunanine (2-Amino-6-oxypurine)

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The pyrimidine bases have a 6-membered ring with two nitrogens and four carbons. Pyrimidines that occur in DNA are cytosine and thymine. Cytosine and uracil occur in RNA. Cytosine (2-oxy-4-amino pyrimidine ) Thiamine(2,4-dioxy-5-methyl pyrimidine ) Uracil (2,4-dioxy pyrimidine )

Naturally Occuring Purines: 

Naturally Occuring Purines Caffeine (coffee) and theobromine (coffee and tea) are naturally occurring purines . Caffeine N N O N N H 3 C O CH 3 CH 3 Theobromine O H N N N N CH 3 CH 3 O

Synthesis Formamide (45 grams) was heated in an open vessel with a condenser for 28 hours in an oil bath at 170-190 °C. After removing excess formamide (32.1 grams) by vacuum distillation, the residue was refluxed with methanol. The methanol solvent was filtered, the solvent removed from the filtrate by vacuum distillation, and almost pure purine obtained; yield 4.93 grams (71% yield from formamide consumed). Crystallization from acetone afforded purine as colorless crystals; melting point 218 °C : 

Synthesis Formamide (45 grams) was heated in an open vessel with a condenser for 28 hours in an oil bath at 170-190 °C. After removing excess formamide (32.1 grams) by vacuum distillation, the residue was refluxed with methanol. The methanol solvent was filtered, the solvent removed from the filtrate by vacuum distillation, and almost pure purine obtained; yield 4.93 grams (71% yield from formamide consumed). Crystallization from acetone afforded purine as colorless crystals; melting point 218 °C

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Fischer Synthesis Adenine

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GUANINE