Ribo-2′-deoxyribo hybrid dinucleoside monophosphates. Proton magnetic resonance studies of 3′,5′- and 2′,5′-uridylyl-2′-deoxythymidine

This 1 Hmr study initiates our examination of the conformations of dinucleoside monophosphates possessing ribo 2′- or 3′-nucleotidyl units linked to 5′-nucleotidyl units possessing the 2′-deoxyribo sugar. The syntheses of uridylyl-3′,5′-2′-deoxythymidine (3′,5′-UpdT) and its 2′,5′-isomer, 2′,5′-UpdT, were carried out with standard techniques. The 1 Hmr data were obtained at frequencies up to 270 MHz and used to derive the dominant conformation of the dimers in aqueous solution. Comparison with data for the component mononucleotides reveals that dimerization does not lead to drastic changes in the molecular conformation. Literature data for dimers possessing only the ribo sugar (3′,5′-UpU) and the 2′-deoxyribo sugar (3′,5′-d(TpT)) are also presented. The results indicate that, at least for our dipyrimidine dimers, the molecular conformation of a particular fragment is not critically dependent on the nature (ribo or 2′-deoxyribo) of the other nucleotide unit.