Further studies on the reaction of adenine, cytosine and corresponding nucleosides with chloroacetaldehyde

It is shown that stable intermediates formed in the reactions of adenine, cytosine and appropriate nucleosides with chloroacetaldehyde have the cyclic carbinolimine structure III. The structural proofs were provided by FD mass spectrometry, elementar analysis, UV and PMR. The kinetics of dehydration was studied on isolated adenosine and cytidine intermediates in the pH range of 3 – 7. It was found that the dehydration process shows rather weak pH dependence in the case of adenosine intermediate, however, this compound dehydrates 6 – 14 times faster in the investigated pH range than cytidine intermediate. When the initial concentration of substrate I /adenosine or cytidine/ was ca. 20 times higher than that normally used in our studies, small quantities of noncyclic carbinolamine II were detected in the first periods of the reaction. Intermediate II is many times less stable than III and decomposes to I during the isolation procedure.