Procedures for the synthesis of protected O2,2′-cyclouridines and their incorporation into dinucleoside monophosphates have been developed. The properties of these molecules with snake venom and spleen phosphodiesterases have been investigated. The cyclonucleotides are easily converted into arabinouridine nucleotides and thus provide a convenient route to these compounds.
The dipole moments of methyl-, ethyl-, 12-propyl-, n-butyl-, 12-amyl-, and phenyl-fluoroformate were determined in dilute benzene solutions at 25 "C. The experimental results suggest that the confornlation of the fluoro-esters is similar to the conformation of the chloro-esters and differs from the conformation of the normal esters; viz. the ester hydrocarbon group and the fluorine atom are cis to each other. Results of fluorine and proton n.m.r. measurements on these molecules support the conclusions based on the dipole moment data if a "through-space" coupling mechanism is assunled for the long range spin-spin coupling JH-F1-5.
The dipole moments of methyl, ethyl, n-propyl, n-butyl, amyl, and phenyl chloroformate as well as n-butyl formate in dilute benzene solution at 25 °C were determined. The experimental results suggest that the configuration of the chloro-esters differs from the configuration of the unchloroinated esters, viz. the ester hydrocarbon group and the chlorine atom are cis to each other.
The dipole morncnts of bron~ochlorornethane, bromodichloromethane, bromotrichloron~ethane, dimethylcarbamyl chloride, dirnethylcarbamyl fluoride, vinyl formate, phenyl chlorothiolforn~ate, y-valerolactone, and 2-iodopropene were determined in dilute benzene solutions at 25 "C. The observed magnitudes of the dipole moments are rationalized in terms of molecular electronic charge distributions.Canadian Journal of Chemistry, 46,523 (1968) Introduction Over the past several years, the nuclear magnetic resonance (n.m.r.) group of the Parker Chemistry Laboratory, University of Manitoba, has investigated the solvent effects on the proton spectra of different molecules (1-4). As is well known, the solvent effect on the proton chemical shift in inolecules may be roughly divided into four main contributions, viz. dispersion forces, electric field forces, and magnetic anisotropy and bulk susceptibility effects. Of these, the electric field effect is strongly dependent on the molecular dipole moment. In order to theoretically calculate the effect of the reaction field, and from the latter, the electric field contribution to the solvent effect, it is necessary to know the dipole moment of the solute molecule. It was for this reason that we measured the dipole momeilts of the above-mentioned molecules. We report our findings here in the hope that they will be of some use to other workers in related or different research fields.
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