Phosphate esters 3-carbon sugars

Acid chlorides are used for the quantitative deterrnination of hydroxyl groups and for acylation of sugars. Industrial appHcations include the formation of the alkyl or aryl carbonates from phosgene (see Carbonic and chloroformic esters) and phosphate esters such as triethyl, triphenyl, tricresyl, and tritolyl phosphates from phosphoms oxychloride. 

The DNA sugar is 2-deoxy-D-ribose. The four heterocyclic bases in DNA are cytosine, thymine, adenine, and guanine. The first two bases are pyrimidines, and the latter two are purines. In nucleosides, the bases are attached to the anomeric carbon (C-1) of the sugar as p-N-glycosides. In nucleotides, the hydroxyl group (-OH) at C-3 or C-5 of the sugar is present as a phosphate ester. 

Nucleosides (e. g. adenosine, cytidine, guanosine, pyrimidine, thymidine, uridine) consist of a nitrogenous purine or pyrimidine base linked to a 5-carbon sugar (ribose or deoxyribose). Nucleotides (adenine, cytosine, guanine, thymine, uracil), the phosphate esters of nucleotides, form the basis of RNA and DNA. As infectious viral nucleic acids, they are capable of penetrating the cells and using available enzyme systems for replication. 

Nucleotides are nucleosides in which one or more phosphate groups are bound to the sugar (Figure 14.23). Most naturally occurring nucleotides are 5 -phosphate esters. If one phosphate group is attached at the 5 -carbon of the sugar, the... 

ATP consists of a nitrogenous base (adenine) and a phosphate ester of the five-carbon sugar ribose (Figure 15.5). The triphosphate group attached to libose is made up of three phosphate groups bonded to one another by phosphoric anhydride bonds. When two phosphate groups react with one another, a water molecule is lost. Because water is lost, the resulting bond is called a phosphoric anhydride, or phosphoanhydride, bond. 

When phosphoric acid is esterified to one of the hydroxyl groups of the sugar portion of a nucleoside, a nucleotide is formed (Figure 9.4). A nucleotide is named for the parent nucleoside, with the suffix -monophosphate added the position of the phosphate ester is specified by the number of the carbon atom at the hydroxyl group to which it is esterified—for instance, adenosine 3 -monophosphate or deoxycytidine 5 -monophosphate. 

Monosaccharides. M. are linear polyhydroxyalde-hydes (aldoses) or polyhydroxyketones (ketoses). Most important among M. are the pentoses (CjHiqO,) and hexoses (C6H,20 ). Important aldopentoses include, e.g., D- ribose, D- xylose, and L- arabinose. Important aldohexoses include D- glucose, D- man-nose, and D- galactose the major ketohexoses are D- fructose and sorbose. The 6- deoxy sugars L- fu-cose and L- L-rhamnose are also widely distributed hexoses. M. with more carbon atoms (heptoses 7 carbon atoms, octoses, etc.) or less carbon atoms (trioses 3 carbon atoms) do not occur in the free form in organisms but do play a role in carbohydrate metabolism as phosphate esters tetroses (4 carbon atoms) erythrose, threose are relatively rate. 

Sulphate groups in sugars are of two kinds, sulphate esters and sulph-amido-groups. The former are simply called sulphates, with the position of the ester indicated by the number of the carbon atom to which it is attached. Galactose -3-sulphate, for example, is common in sulphated galactosphingo-lipids. (Similar rules apply with phosphate ester groups.)... 

The sugars are in the furanose form. They are linked through the hydroxy groups on carbons 3 and 5 as phosphate esters. The heterocyclic amine bases are attached at carbon 1, replacing the hydroxy group. 

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