| Abstract
| - Recently, we have proposed a new concept for cross-linking agents with inducible reactivity, inwhich the highly reactive cross-linking agent, the 2-amino-6-vinylpurine nucleoside analogue (1),can be regenerated in situ from its stable precursors, the phenylsulfide (4) and the phenylsulfoxide(3) derivatives, by a hybridization-promoted activation process with selectivity to cytidine. Thephenylsulfide precursor (4) exhibited cross-linking ability despite its high stability toward strongnucleophiles such as amines and thiols. In this study, we investigated the substituent effects ofthe phenylsulfide group on the cross-linking reaction, and determined the 2-carboxy substituent ofthe phenylsulfide derivative (11k) as an efficient cross-linking agent with inducible reactivity.Detailed investigations have shown that the phenylsulfoxide (3) and phenylsulfide (4) precursorsproduce the 2-amino-6-vinylpurine nucleoside (1) as the common reactive species. It has beenconcluded that the nature of the inducible reactivity of the precursors (3 and 4) is acceleration oftheir elimination to the 2-amino-6-vinylpurine nucleoside (1) through the selective process in theduplex with the ODN having cytidine at the target site.
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