Esters biologically significant reactions

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... 

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... 

Thiol esters are better acylating agents than oxygen esters and such reactions are of some biological significance. Studies by Bruice and his coworkers have indicated that the pattern of thiolester... 

All the features of the reaction discovered by Brenner are analogous to the transpeptidation reaction proposed by Fruton. There is no information, at present, on the possible biological significance of this type of peptide synthesis via amino acid esters. 

Wessjohann s group reported a one-pot synthesis of tryptophane DKPs [37]. This combination of two biologically highly active moieties was achieved in a one-pot variation of the UDC protocol (Scheme 4). It was shown that, assisted by microwave irradiation, the reaction times can be reduced significantly and that the formation of DKPs occurs even without the necessity to activate the ester. By employing microwave (dielectric) heating, the reaction times were reduced substantially. 

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