Regioselective Cleavages of 2', 3'-Cyclic Phosphates of Ribonucleotides Induced by Cyclod e x t r i n s and Their Derivative s

Abstract

Regioselective cleavages of 2', 3'-cyclic m onophosphateso f cytidine (Ia), uri dine (Ib), adenosine (Ic), and guanosine (Id) are achieved by cyclodextrins (CyDs) as catalysts. α-CyD promotes the cleavages of the P-O(2') bonds, resulting in the selective formation of the corresponding 3'-phosphates. At the concentration 0.05 M of α-CyD, the- selectivities are 98, 94, 76, and 67% for the cleavages of Ia-d. In the absence of α-CyD, however, concurrent cleavages of the P-0(3') bonds singificantly take place and the selectivities are only around 50%. In contrast with the regioselectiveP -0(2') cleavages by α-CyD, β-CyD and γ-CyDs enhance the cleavages of the P-0(3') bonds. The selectivity for the formation of adenosine 2'-phosphate from Ic is 88% at the concentration 0.015 M of β-CyD. The dominant effect of the molecular size of CyD on the regioselective catalysis is interpreted in terms of the difference of the structure of the CyD complex. Regioselective cleavages of the dimers and the polymers of ribonucleotides, which proceed via the cyclic phosphates as intermediates, are also successfully carried out by use of CyDs. The catalytic activities of CyDs have been promoted still more by the chemical modification.