title: Ureidopyrimidinones incorporating a functionalizable p-aminophenyl electron-donating group at C-6.
abstract: [structure: see text] 2-Ureido-4-[1H]-pyrimidinones have been reported to dimerize via quadruple hydrogen bonding systems with dimerization constants >10(6) M(-1) in CDCl3. The dimerization constant, K(dim), is dependent on the solvent as well as the ring-substituents present, where previously alkyl (e.g., R1 = Me) and aromatic moieties (e.g., R1 = p-NO2C6H4, R1 = C6H2(OC13H27)3) have been incorporated at the C-6 position. To assess the influence of alternative, functionalizable, electron-donating groups on the dimerization motif and tautomeric distribution of isomers, the synthesis of compounds possessing aminophenyl functionality at the C-6 position has been achieved. NMR spectroscopy chemical shift analysis revealed that compound 2 (R1 = p-NH2C6H4, R2 = C6H13) existed as the 2-ureido-4-pyrimidinol dimeric DADA array in DMSO-d6, where a dimerization constant of 46 M(-1) was determined. This is the first time that a ureidopyrimidinone quadruple hydrogen bonding DADA array has been observed in pure DMSO, a highly polar solvent. The azo-derivative 5 of compound 2 was prepared which also adopted the pyrimidin-4-ol form in DMSO-d6. Compounds 7, 10 and 11 were then synthesized containing a more hydrophilic PEG unit in the lateral chain and the tautomeric distributions were determined.
authors.affiliation: Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, UK.
authors.forename: Valerie G H
authors.initials: VG
authors.lastname: Lafitte
authors.forename: Abil E
authors.initials: AE
authors.lastname: Aliev
authors.forename: Helen C
authors.initials: HC
authors.lastname: Hailes
authors.forename: Kason
authors.initials: K
authors.lastname: Bala
authors.forename: Peter
authors.initials: P
authors.lastname: Golding