Polynucleotides. XII. Synthesis and Properties of Dinucleoside Monophosphates containing 8-Bromoadenosine

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Attempt to obtain 8-bromoadenylyl-(3'-5')-8-bromoadenosine (BrApBrA) (III) by the condensation of N⁶, O^2', O^3'-tribenzoyl-8-bromoadenosine 3'-phosphate (V) and 2', 3'-O-ethoxymethylidene-8-bromoadenosine (VI) using dicyclohexylcarbodiimide (DCC) gave 8-oxyadenylyl-(3'-5')-8-bromoadenosine (HOApBrA) (VII) after removal of protecting groups. Structure of VII was confirmed by ultraviolet (UV) and circular dichroism (CD) spectra as well as enzymatic hydrolysis. Condensation of N⁶, O⁵-diacetyl-8-bromoadenosine 2'(3')-phosphate (IVa) and compound VI using diphenylphosphorochloridate gave 2'-5'(X) and 3'-5'(III) isomers of 8-bromoadenylyl-8-bromoadenosine, which were separated and purified by column chromatography, paper electrophoresis and paper chromatography. Structure of compounds X and III was elucidated by optical properties and enzymatic digestions. Hypochromicities of X and III were 14% and 10%, respectively. From the CD spectra of both compounds, a syn-syn, left-handed structure of these dinucleoside monophosphates was predicted.