Sugar phosphates stable esters

Nucleic acids store genetic information. They are polymers whose building blocks (monomers) are the nucleotides, themselves made of three parts—a heterocyclic base, a sugar, and a phosphate ester. In the example below, adenine is the base (shown in black), adenosine is the nucleoside (base and sugar), and the nucleotide is the whole molecule (base + sugar + phosphate). This nucleotide is called AMP—adenosine monophosphate. Phosphates are key compounds in nature because they form useful stable linkages between molecules and can also be built up into reactive molecules by simply multiplying the number of phosphate residues. The most important of these nucleotides is also one of the most important molecules in nature— adenosine triphosphate or ATP. 

Furthermore, the GPO procedure can also be used for a preparative synthesis of the corresponding phosphorothioate (37), phosphoramidate (38), and methylene phosphonate (39) analogs of (25) (Figure 10.20) from suitable diol precursors [106] to be used as aldolase substrates [102]. In fact, such isosteric replacements of the phosphate ester oxygen were found to be tolerable by a number of class I and class II aldolases, and only some specific enzymes failed to accept the less polar phosphonate (39) [107]. Thus, sugar phosphonates (e.g. (71)/(72)) that mimic metabolic intermediates but are hydrolytically stable to phosphatase degradation can be rapidly synthesized (Figure 10.28). 

Nucleosides and nucleotides are combinations of a base with a sugar. A nucleoside is an N-glycoside formed between a base and a sugar (usually ribose or deoxyribose). A nucleotide is a phosphate ester of a nucleoside. DNA nucleotides are more stable to acid hydrolysis of the glycosidic bond, which is one reason tfrat DNA has superceded RNA as the main genetic storage molecule it is less prone to mutation. 

Covalent cross-linking by way of non-saccharide molecules, other than phosphate and sulphate, probably does occur and there are two classes of residue that might well be involved, which are borate and silicate. Borate is the less likely of the two, since its esters with sugars and other polyols are stable only at fairly high pH and it tends to form internal esters with sugars rather than cross-linking them. However, in special environments it might cross-link symmetrically. 

The use of phosphorus oxychloride for the synthesis of phosphate esters of sugars 160) has been largely replaced by dibenzyl 161) and diphenyl phosphorochloridates 162), The latter reagent may be prepared in a pure, stable form which reacts readily with an alcohol in pyridine at low temperature. The phenyl groups may be removed from the resulting di-0-phenyl phosphate derivative of the alcohol by catalytic hydrogenation employing a platinum catalyst. 

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