title: Synthetic studies on novel 1,4-dihydro-2-methylthio-4,4,6-trisubstituted pyrimidine-5-carboxylic acid esters and their tautomers.
abstract: A mixture of alkyl 1,4-dihydro-2-methylthio-4,4,6-trisubstituted pyrimidine-5-carboxylate 1 and its tautomeric isomer, alkyl 1,6-dihydro-2-methylthio-4,6,6-trisubstituted pyrimidine-5-carboxylate 2 is synthesized by the Atwal-Biginelli cyclocondensation reaction of S-methylisothiourea hemisulfate salt 3 with 2-(gem-disubstituted)methylene-3-oxoesters 4 that can be accessed by the Lehnert procedure for the Knoevenagel-type condensation. The structures of the tautomeric products of the Atwal-Biginelli cyclocondensation reaction, 1 and 2, which are inseparable from each other, are determined unambiguously by (1)H-NMR spectroscopy at various temperatures and nuclear Overhauser enhancement spectroscopy (NOESY) experiment. Because these dihydropyrimidine products are otherwise inaccessible and thus hitherto unavailable, the synthetic methods established in this study will help to expand the molecular diversity of their related derivatives.
authors: Department of Pharmaceutical Chemistry, Faculty of Pharmacy, Yasuda Women's University, Hiroshima 731–0153, Japan. nishimura-y@yasuda-u.ac.jp
authors: Yoshio
authors: Y
authors: Nishimura
authors: Yasuko
authors: Y
authors: Okamoto
authors: Masaya
authors: M
authors: Ikunaka
authors: Yoshihiko
authors: Y
authors: Ohyama
mesh_terms: D002264:Carboxylic Acids / Q000138:chemical synthesis* / Q000737:chemistry; D060326:Chemistry Techniques, Synthetic; D003500:Cyclization; D004952:Esters / Q000737:chemistry; D007536:Isomerism; D007550:Isothiuronium / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D011743:Pyrimidines / Q000138:chemical synthesis* / Q000737:chemistry
chemical_list: D002264:Carboxylic Acids; D004952:Esters; D011743:Pyrimidines; D007550:Isothiuronium; C027744:S-methylisothiopseudouronium