Esters biologically significant

Several methods for the preparation of the parent compound in this system, tris(trimethylsilyl)phosphite, have been reported.114 118 The application of this and related reagents in reaction with alkyl halides has been reported and used for the preparation of a variety of phosphonic acid analogues of phospholipids.114119-124 Interestingly, alkyl chlorides appear to be more reactive with the silyl reagents than do alkyl iodides, a reversal of the normally observed trend with alkyl esters of the phosphorus acids. (The particular use of silyl phosphorus reagents for the synthesis of biologically significant compounds has... 

The female produced long range sex pheromone of Migdolus fryans is AT-[(2 S)-2-methylbutyl]-(2S)-2-methylbutyramide 185 [345]. The acyl part as well as the alkyl part may be derived from isoleucine. Interestingly, this amide is accompanied by the ethyl ester of N-formyl isoleucine, which is also known from the scarab beetle, Phyllophaga elenans [181]. This amino acid derivative proved to be not attractive for both species its biological significance remains to be clarified. 

Since the use of human plasma as a model for skin esterases is debatable, the relevance of the biological results in Table 8.6 need validation as far as skin delivery is concerned. Indeed, permeation experiments across excised human skin showed that administration of prodrugs markedly improved the cutaneous delivery of nalidixic acid, with complete hydrolysis of the (acyl-oxy)methyl esters and significant, albeit incomplete, hydrolysis of the methyl and carbamoylmethyl esters [64],... 

Phosphate esters, particularly AMP, ADP and ATP, have vital biological functions and this fact has generated intense interest in their reaction mechanisms. Subtle stereochemical experiments, such as the use of isotopically chiral compounds, have been important and, since all biological phosphorylation reactions appear to involve metal ion catalysis, the stereochemistry of phosphate ion coordination has also been subject to much attention.229,230 Apart from its biological significance, this work has revealed some interesting contrasts with the stereochemistry of ligand systems in which saturated carbon units link the donor atoms. 

Although transfer of the acetate group from its inital site, bound as a serine ester, to its reactive position on Cys-1305(a) can occur via an intermediate in which the acetate is attached to the phosphopantetheine thiol, evidence suggests that this reaction is not kinetically competent and that the biologically significant mechanism utilizes a direct transfer from Ser-819( ) to Cys-1305(a) [73]. Transfer of the malonyl group from its initial position at Ser-5421 (/3) to its reactive position as a phosphopantetheine thioester occurs directly [69]. 

Considerable study has been devoted to the reactions of dinucleotides and related molecules, like those in Fig. 10, because of the biological significance of RNA and interest in the mechanism of RNase, which catalyzes its cleavage. The /Jlg values were measured for the cyclization reaction of a series of aryl esters 10A (to yield a 2, 3 cyclic phosphate) under alkaline conditions. For the imidazole general... 

In this work it was reported that the biological activity and residual properties of biphenyl-3-ylmethyl (1R,S)-cis-3-(2,2-di-chlorovinyl)-2,2-dimethylcyclopropanecarboxylate were about one-half that of the corresponding 3-phenoxybenzyl ester. The preparation of a series of substituted derivatives of biphenyl-3-ylmethyl (1R,S)-cis-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane-carboxylates resulted in esters with significantly greater insecticidal activity and broader spectrum of biological activity than the conventional pyrethroid insecticides(7). The 2-monosubstituted derivatives were found to be the most active compounds in this series with the 2-methyl compound being the most active. This result encouraged us to combine these biphenyl-3-ylmethyl compounds with alkyl aryl methanone oximes. 

Lange LG, Mechanism of fatty acid ethyl ester formation and biological significance. Ann NY Acad Sci 1991 625 802-806. 

A whole class of fascinating, acidic and ester polysaccharides of biological significance awaits exploration by x-ray diffraction. Typical of these compounds are the pneumococcal polysaccharides, whose structures are highly specific, albeit they contain a wide variety of carbohydrate moieties, of which D-glucuronic acid is a common one. Occasionally, a phosphoric ester link between moieties is an integral part of the complex, repeating... 

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