Phosphoric diesters

Many bacterial polysaccharides contain phosphoric ester groups. There is a limited number of examples of monoesters. More common are phosphoric diesters, connecting an amino alcohol or an alditol to the polysaccharide chain. Another possibility is that oligosaccharide or oligosaccharide-alditol repeating units are connected to a polymer by phosphoric diester linkages. In addition to the intracellular teichoic acids, several bacteria, for example, different types of Streptococcus pneumoniae, elaborate extracellular polymers of this type. These polymers are generally discussed in connection with the bacterial polysaccharides. 

In some polysaccharides, the reducing terminal is linked, through a phosphoric diester linkage, to O-1 of a 2,3-di-6 -acylglycerol. This structural feature has been demonstrated for some capsular polysaccharides from E. coli and Neisseria species, - but is probably more common than that. Non-covalent linkage between the lipid part and the cell membrane may explain why extracellular polysaccharides often occur as capsules, and the high (apparent) molecular weight observed for these polysaccharides may be due to micelle formation in aqueous solution. 

In different polysaccharides of the teichoic acid type, monosaccharides or oligosaccharides are connected by phosphoric diester linkages. Two examples are the capsular antigens from Neisseria meningitides type A (56) and Haemophilus influenzae type c (57), respectively. Glycerol phosphate... 

Polycondensation of amino acids with phosphorous diester triazolide are described in references [28] and [53]. Below 80 °C, no racemization was found. 

Other polypeptides obtained by polycondensation with phosphorous diester triazolides are N6-Z-polylysine,[28] Na-Z-isopolylysine,t281 and the sequence polypeptides from /J-Ala-/J-Ala-Gly.l53]... 

Alcohols can be phosphorylated to phosphoric diesters by ionic phosphoric monoimidazolides in acetone at temperatures of about 50-60 °C over the course of several hours. These imidazolides are generally prepared by reaction of the appropriate phosphate with CDI (see Section 2.2). Reactions with ethyl, -butyl, w-pentyl, -octyl benzyl alcohol and various other alcohols have also been described.[1]... 

Adenosine and uridine monosphophate (AMP and UMP, resp.) react via their imi-dazolides with alcohols to give the phosphoric diesters ... 

With neutral phosphoric monoimidazolides, which are more reactive than the ionic species the reaction time for phosphorylation of an alcohol is reduced. A one-flask synthesis of unsymmetrical phosphoric diesters from N-( 1,2-dimethylethylenedioxy-phosphoryl)imidazole, prepared from di(l,2-dimethylethylene)pyrophosphate and imidazole, is presented below [103,[11]... 

By using a phosphoric diester monotetrazolide, made in situ from the corresponding phosphoric chloride and tetrazole in the presence of triethylamine, die 3 -OH of a suitably protected nucleoside could be phosphorylated to give a fully protected nucleotide [241... 

Fully protected nucleotides could also be prepared with a phosphoric diester chloride/ Af-methylimidazole combination, probably via a phosphoric imidazolium intermediate 1253... 

The phosphitylation agent A-tetrazolyldiethoxyphosphine (phosphorous diester tetrazolide) can be made in situ from diethoxydiisopropylaminophosphine and two moles of tetrazole (tetrazole activation of phosphoramidites). 961... 

With 3-hydroxypropionic or 4-hydroxybutyric acid very little or no phosphor diester bond formation occurred. 1753... 

A labeled phosphoric acid triester is formed by phosphorylation of an alcohol with a labeled phosphoric diester imidazolide [187],[188]... 

A phosphitylation instead of an azole transfer occurred in the reaction of a guanosine derivative with phosphorous diester tetrazolide (diethoxytetrazolylphosphine) [2003,[2013... 

A novel synthesis of D-glucose 6-phosphate (in 55% yield) has been reported it involves alcoholysis of the cyclic phosphate of catechol with 1,2-O-isopropylidene-a-D-glucofuranose, followed by acid hydrolysis of the so-formed phosphoric diester.192 The reagent... 

O-Phosphonomannans containing phosphoric diester bridges lend themselves to a similar approach, as 13C-C-0-31P couplings may be interpreted in the same way. This subject is discussed in Section VI,8. 

Initially, the O-phosphonomannan was assigned a repeating unit of 2-0-/8-D-mannopyranosyl-a-D-mannopyranose joined by (1— -phosphoric diester bridges (30). With a- and /8-D-mannopyranosyl units, it... 

No phosphate was released when the fraction was treated with phosphomonoesterase, indicating the presence of a phosphoric diester. Hydrolysis of the unknown KDO derivative (1 M HC1 for 5 h at... 

Phosphatases of documented or potential interest in the context of this book include phosphoric monoester hydrolases (EC 3.1.3), phosphoric diester hydrolases (EC 3.1.4), and phosphoric triester hydrolases (EC 3.1.8). 

Phosphatases are numerous and important enzymes (see also Chapt. 2). They are classified as phosphoric monoester hydrolases (phosphatases, EC 3.1.3), phosphoric diester hydrolases (phosphodiesterases, EC 3.1.4), triphosphoric monoester hydrolases (EC 3.1.5), diphosphoric monoester hydrolases (pyrophosphatases, EC 3.1.7), and phosphoric triester hydrolases (EC 3.1.8) [21] [63]. Most of these enzymes have a narrow substrate specificity restricted to endogenous compounds. However, some of these enzymes are active toward xenobiotic organophosphorus compounds, e.g., alkaline phosphatase (EC 3.1.3.1), acid phosphatase (EC 3.1.3.2), aryldialkylphosphatase (para-oxonase (PON1), EC 3.1.8.1) and diisopropyl-fluorophosphatase (tabunase, somanase, EC 3.1.8.2) [64 - 70]. However, such a classification is far from definitive and will evolve with further biochemical findings. Thus, a good correlation has been found in human blood samples between somanase and sarinase activities on the one hand, and paraoxonase (PON1) type Q isozyme concentrations on the other [71]. 

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