Thymidine esterification

A.7.1 Esterification of Acids using Carbodiimides. The formation of anhydrides from carboxylic acids, thiocarboxylic acids, sulfonic acids and phosphorous acids are discussed in Section 2.4.S.2. In this section only special cases of anhydride formation are described. Mixed anhydrides of amino acids and adenylic acid are produced from the corresponding acids using DCC as the condensation agent. ° Mixed anhydrides not containing amino acids, such as butyryl adenate, adenosine 5 -phosphosulfate and p-nitrophenyl-thymidine-5-phosphate are also obtained. 

The overall efficiency of these nonmolecular bimetallic sysems to promote phosphate ester hydrolysis was illustrated with ApA as RNA model (0.1 mM) hydrolysis occurred with a mixture of LaCls and FeCls (10 mM each) to more than 70% at 50°C and neutral pH in 5 min (351). The products of the reaction included adenosine and 2 -and 3 -monophosphate adenonsine, indicating that the mechanism involved a first trans-esterification step by the vicinal 2 -OH of ribose. With the same mixture of metal ions, the DNA model TpT (0.1 mM) (Fig. 18), left, B = thymine) was converted to thymidine and 3 - and 5 -monophosphate th5miidine with 36% of conversion in 24 hr at 70°C at neutral pH. The important point is the notion of cooperativity between the two metals. 

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