Sugar nucleotides tris

M. Nomura, K. Endo, S. Shuto, and A. Matsuda, Nucleosides and nucleotides. 191. Ring expansion reaction of l-[2,3,5-tri-0-TBS-4 alpha-formyl-beta-D-ri o-pentofuranosyl] uracil by treating with (methylene)triphenylphosphorane to give a new nucleoside containing dihydrooxepine ring at the sugar moiety, Tetrahedron, 55 (1999) 14847-14854. 

There is another pnrine derivative of crucial biochemical importance - adenosine triphosphate (ATP). This substance is a carrier of energy, for when a phosphate link is broken, a large amount of energy is released. Note some trivial nomenclature the moieties produced by linking one of the heterocyclic bases to a ribose or 2 -deoxyribose sugar, are known as nucleosides (e.g. adenosine, guanosine, cytidine, thymidine). A nncleotide is a 5 -phosphate (or di- or tri-phosphate) of a nucleoside - ATP is a nucleotide. 

Nucleotides differ from nucleosides in that the latter do not contain phosphate, so we sometimes refer to nucleotides as nucleoside (mono,di, or tri)-phosphates. For example, adenosine diphosphate is a nucleotide (also called ADP) Deoxyribonucleotides (written with a d ) differ from ribonucleotides in containing deoxyribose as the sugar moiety instead of ribose. In some naming schemes, deoxythymidine nucleotides are written without the d, but the d convention will be used here. 

In addition to the sugar component, at the 5 position of the ribose, nucleotides contain a mono-, di-, or tri-phosphate group. 

The nucleotides which consist of three parts, namely a nitrogenous base, a pentose sugar and a phosphate radical, are a very important group of compounds since one or more of them is involved in virtually every biochemical process. The adenosine di- and tri-phosphates which play an essential part in cellular energy exchanges have a nucleotide-type structure as do many of the coenzymes. Furthermore, nucleotides constitute the monomeric units of which the nucleic acids are composed that is to say nucleic acids are polynucleotides. The nucleic acids which are of two types, deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), are responsible for directing the synthesis of proteins. They specify the unique sequence of amino acids in any particular protein and consequently should be regarded as primordial molecules on whose existence that of the proteins depends. However, since the synthesis of the nucleic acids depends on enzymes which are themselves proteins, this poses the fundamental evolutionary question as to which came first - the biochemical version of the problem of the chicken and the egg ... 

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