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[摘要]：The thioinethylene-linked U*[s]U-(*) dimers 9-14 were synthesized by substitution of the 6[(mesyloxy)methyl]uridine 6 by the thiolate derived from the uridine-5'-thioacetates 7 and 8 followed by O-deprotection. Similarly, the thiomethylene-linked A*[s]A((*)) dimers 9-14 were obtained from the 8-(broniomethyl)adenosine 15 and the adenosine-5'-thioacetates 16 and 17. The concentration dependence of both H-N(3) of the U*[s]U-(*) dimers 9- 14 evidences the formation of linear and cyclic duplexes, and of linear higher associates, C(8 or 6)CH,OH and/or C(5'/II)OH groups favouring the formation of cyclic duplexes. The concentration dependence of the chemical shift for both H2N-C(6) of the A*[s]A(0 dimers 18-23 evidences the formation of mainly linear associates. The heteroassociation of U*[s]U-(*) to A*[s]A(*) dimers is stronger than the homoassociation of U*[s]U(*) dimers, as evidenced by diluting equimolar mixtures of 11/20 and 13/22. A 1:1 stoichiometry of the heteroassociation is evidenced by a Job's plot for 11/20, and by mole ratio plots for 9/18, 10/19, 12/21, 13/22, and 14/23. |
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