Synthesis of 6-alkyluridines from 6-cyanouridine via zinc(II) chloride-catalyzed nucleophilic substitution with alkyl Grignard reagents

A Regioselective Synthesis of 6-Alkyl- and 6-Aryluracils by Cs2CO3- or K3PO4-Promoted Dimerization of 3-Alkyl- and 3-Aryl-2-Propynamides

A regioselective synthesis of 6-alkyl- and 6-aryluracils was developed by the dimerization of 3-alkyl- and 3-aryl-2-propynamides promoted by either Cs₂CO₃ or K₃PO₄. A range of 3-aryl-2-propynamides, with both electron-deficient and electron-rich 3-aryl substituents, were successfully reacted in high yields. Cs⁺ acts as a soft Lewis acid to polarize the carbon-carbon triple bond, and solid K₃PO₄ interacts with carbonyl oxygen, promoting intermolecular nucleophilic attack by the only weakly nucleophilic amide nitrogen. Experiments were conducted to support the proposed mechanism.

The first structurally analysed nucleic acid building block containing the Reese protecting group: 2'-O-[1-(2-fluorophenyl)-4-methoxypiperidin-4-yl]-β-D-(1'R,2'R,3'R,4'R)-uridine

The title compound, C21H26FN3O7, is assembled by N-H...O and O-H...O hydrogen bonds into well-separated two-dimensional layers of about 15 Å thickness. The crescent conformation of the molecules is stabilized by weak intramolecular C-H...O and C-H...F hydrogen bonds. The uridine moiety adopts an anti conformation. The ribofuranose ring exists in an envelope conformation. All the endocyclic uracil bonds are shorter than normal single C-N and C-C bonds, and five of them have comparable lengths, which implies a considerable degree of delocalization of the electron density within this ring.