Nucleosides in nucleic acids are formed by the condensation of purine or pyrimidine bases with ribose or deoxyribose. A glycosidic bond is formed between the carbon atom (C1) in the ribose molecule and the nitrogen atom (N1) in the pyrimidine molecule or the nitrogen atom (N9) in the purine molecule to generate N-glycosides, that is, the ribofuranoside of pyrimidine or purine, called for ribonucleosides. A glycosidic bond is formed between the carbon atom (C1) in the 2-deoxyribose molecule and the nitrogen atom (N1) in the pyrimidine molecule or the nitrogen atom (N9) in the purine molecule to become the furanoside of pyrimidine or purine, called Deoxyribonucleosides. For example, adenine is attached to ribose to make adenine-9-β-D-ribofuranoside, called adenosine; thymine is attached to 2′-deoxyribose to make thymine-1-β- D-2'-deoxyribofuranoside, known as thymidine.