64018-52-6Relevant academic research and scientific papers
One-pot synthesis of acyclic nucleosides from carbohydrate derivatives, by combination of tandem and sequential reactions
Boto, Alicia,Hernandez, Dacil,Hernandez, Rosendo,Alvarez, Eleuterio
, p. 9523 - 9532 (2008/03/28)
(Chemical Equation Presented) The design of processes which combine tandem and sequential reactions allows the transformation of readily available precursors into high-profit products. This strategy is illustrated by the one-pot synthesis of acyclic nucle
Kinetic solvent deuterium isotope effect in transesterification of RNA models
Virtanen, Noora,Polari, Lauri,Vaelilae, Maria,Mikkola, Satu
, p. 385 - 397 (2007/10/03)
2-Methylbenzimidazole ribonucleoside arylphosphates (1a,b) and alkylphosphates (2a,b) were synthesized as RNA model compounds containing a minimised number of exchangeable protons. Intramolecular transesterification of these substrates was studied in H2O and D2O solutions over a wide pL range and apparent kinetic solvent deuterium isotope effects of the alkaline cleavage of both substrates and of the cleavage and isomerisation of 2a under neutral and acidic conditions were determined. The observed K H2O/kD2O of 4.9 obtained for the alkaline cleavage of the arylphosphate 1b can be primarily attributed to the ΔpK of the attacking nucleophile. The alkyl leaving group in 2a brings about an additional 1.5-fold isotope effect (kH2O/kD2O of 7.1 observed), which, considering the pL-dependence of the reaction, can not be explained by a process involving a proton transfer. Differences in solvation of the transition state are tentatively suggested as a source of the difference. In contrast to alkaline cleavage, under neutral and acidic conditions the cleavage and isomerisation of 2a showed no apparent solvent isotope effect. Several examples found in the literature show that intramolecular proton transfer from phosphate to the leaving group in pre-equilibria may not necessarily result in an observable solvent isotope effect. This may also explain the results obtained in the present work, since intramolecular proton transfer processes take place in transesterification reactions of 2a under neutral and acidic conditions. Relevance of the results obtained in the base catalysed cleavage to hammerhead ribozyme reaction is briefly discussed. Copyright
Alkoxyl Migration in Displacement of a 5-Trifluoromethanesulfonyloxy Group from Ribofuranosides
Iyer, Vaidyanathan K.,Horwitz, Jerome P.
, p. 644 - 649 (2007/10/02)
Methyl 2,3-O-isopropylidene-5-O-triflyl-β-D-ribofuranoside (2) reacts at room temperature with primary aralkanols such as benzyl alcohol and the steroid alcohols 3a,b in dichloromethane and in the presence of sodium sulfate to give the corresponding aralkyl 2,3-O-isopropylidene-5-O-methyl-β-D-ribofuranosides 5a,b and 11 in 40-45percent yields.Migration of the methoxyl group from C-1 to C-5, via a tricyclic oxonium ion (7a), is suggested as the basis of formation of the new β-glycoside.Anchimeric assistance by a benzyloxy group in the displacement of the sulfonate is observed in the reaction of benzyl 2,3-O-isopropylidene-5-O-triflyl-β-D-ribofuranoside (14) with methanol, which affords methyl 5-O-benzyl-2,3-O-isopropylidene-β-D-ribofuranoside (15) in 40percent yield on treatment with Na2SO4 in CH2Cl2.The elements of anomeric control in these facile transformations remain to be elaborated.
