SYNTHESIS AND KINETIC-STUDY OF THE DEAMINATION OF THE CIS DIASTEREOMERS OF ,6-DIHYDROXY-5,6-DIHYDRO-5-METHYL-2'-DEOXYCYTIDINE

The main objectives of the present work were the synthesis of the two cis diastereomers of ,6-dihydroxy-5,6-dihydro-5-methyl-2'-deoxycytidin e and the kinetic study of their hydrolytic deamination. The preparati on of the two glycols, two main (OH)-O-.-mediated oxidation products o f 5-methyl-2'-deoxycytidine, was achieved in two steps. The first one involved the synthesis of the two trans-(5R,6S)- and o-6-hydroxy-5,6-d ihydro-5-methyl-2'-deoxycytidine. In a subsequent step, the bromohydri ns were specifically converted into the cis-(5S,6S) and (5R,6R) diaste reomers of 6-dihydroxy-5,6-dihydro-5-methyl-2'-deoxycytidine, respecti vely, under slightly alkaline conditions. The resulting glycols were p urified by reverse phase high performance liquid chromatography and ch aracterized by extensive spectroscopy measurements including C-13- and H-1-NMR analyses. Exact mass determination was Inferred from high res olution fast atom bombardment mass spectrometry measurements. Circular dichroism spectroscopy confirmed the diastereomeric relationship exis ting between the pair of glycols. Kinetic study of the deamination of the above glycols was carried out in phosphate buffer solutions (pH 7) at two different temperatures (37 degrees C and 25 degrees C) in orde r to determine the thermodynamic and kinetic parameters of the reactio n.