The origin of life is believed to have started with prebiotic molecules reacting along unidentified pathways to produce key molecules such as nucleosides. To date, a single prebiotic pathway to purine nucleosides had been proposed. It is considered to be inefficient due to missing regioselectivity and low yields. We report that the condensation of formamidopyrimidines (FaPys) with sugars provides the natural N-9 nucleosides with extreme regioselectivity and in good yields (60%). The FaPys are available from formic acid and aminopyrimidines, which are in turn available from prebiotic molecules that were also detected during the Rosetta comet mission. This nucleoside formation pathway can be fused to sugar-forming reactions to produce pentosides, providing a plausible scenario of how purine nucleosides may have formed under prebiotic conditions.

was also 10-4 M in leuco crystal violet and 2 X 10~1 234 M in toluenesulfonic acid. From the amount of crystal violet dye obtained as determined spectrally, and from the reaction stoichiometry (1 mol of dye per biimidazole dissociated) and quantum yield of unity,9 both experimentally determined, radical concentration immediately after the flash was obtained.Rates of Triarylimidazolyl Radical Dimerization.-A Perkin-Elmer "Spectrachord" Model 400A was set up in a dark room to record absorbance (at of each radical) vs. time. A solution of biimidazole in carefully purified benzene was irradiated until a steady state was established and absorbance was recorded for several half-lives and determined eventual!)-at "t = ® ." From the usual second-order expression, the slope of 1/A. plotted vs. t gave k/e (cell length = 1 cm) reported in Table I. From these values k was calculated.Extreme care was necessary to free solvents of impurities which react with radicals. Normally, three distillations of reagent grade solvent sufficed. Even with carefully purified solvents, radical dimerization was not the exclusive fate of radicals in the media studied. A small but detectable deviation from strict second-order was apparent sometime during the second half-life4 and A" was slightly greater than A measured prior to irradiation. Rate constants were taken from the first half-life.Rates in 50:50 vol methanol-benzene were measured both in the spectrometer and in the flash photolysis apparatus used to determine extinction coefficients. An oscillographic trace of absorbance vs. time was photographed.

The synthesis of a variety of a-branched trifluoroethyl amines was achieved by reaction of N-aryl hemiaminal ethers with organomagnesium reagents.

An operationally simple one-pot reaction for the preparation of a novel class of racemic trifluoromethylated 2,3-dihydro-1H-imidazoles derived from electron-poor N,O-acetals and aryl Grignard reagents is described. In addition, access to highly functionalized 2-trifluoromethyl-2,3-dihydro-1H-imidazoles was accomplished by reaction of N-aryl hemiaminal ethers and N-aryl trifluoroethylamines in the presence of an excess of n-butyllithium.

No abstract

Much research effort has been devoted to the synthesis of fluorinated organic compounds in medicinal chemistry programs. For instance, incorporation of fluorine substituents and trifluoromethyl groups has become a widespread lead optimization strategy owing to the often favorable influence of such moieties on affinity and physicochemical properties. However, introduction of fluoroalkyl groups into dedicated positions of pharmacophores is synthetically challenging. In particular, efficient syntheses of di-and trifluoroethylamines are needed as

No abstract

The title compounds are obtained by addition of functionalized Grignard reagents to di‐ and trifluoromethylated N‐aryl‐substituted N,O‐acetals.