title: Synthesis and structural characterization of pyrimidine bi- and tricyclic nucleosides with sugar puckers conformationally locked into the eastern region of the pseudorotational cycle.
abstract: Reaction of 5'-O-tosyl TSAO-m(3)T (1) with amines has led to the synthesis of new classes of bi- and tricyclic nucleosides. Full details about the synthesis of these compounds and a plausible mechanism to explain their obtention are reported. In addition, we describe the development of a second, more efficient, and higher yielding synthetic route as a general approach for the synthesis of some of these bicyclic nucleosides. To study the conformational behavior of the bi- and tricyclic nucleosides described in this paper, intensive NMR investigations and molecular modeling studies were performed. Conformational analysis indicates that the furanose ring of the compounds described here prefers the eastern side of the pseudorotation cycle with the base substituents preferentially in the anti range. The torsion angle gamma describing the C-4'[bond]C-5' is found to prefer the +sc range. These compounds represent a novel class of E-type conformationally restricted bicyclic ribo-nucleosides containing a [3.3.0]-fused carbohydrate moiety. The bicyclic nucleosides described herein present an interesting potential for diverse and selective chemical treatments on the 2'-hydroxyl and/or the functionalities incorporated at the bridge between C-3' and C-5'.
authors.affiliation: Instituto de Química Médica (CSIC), Juan de la Cierva 3, 28006 Madrid, Spain.
authors.forename: Cristina
authors.initials: C
authors.lastname: Chamorro
authors.forename: Santos M
authors.initials: SM
authors.lastname: Luengo
authors.forename: María-Cruz
authors.initials: MC
authors.lastname: Bonache
authors.forename: Sonsoles
authors.initials: S
authors.lastname: Velázquez
authors.forename: María-Jesús
authors.initials: MJ
authors.lastname: Pérez-Pérez
authors.forename: María-José
authors.initials: MJ
authors.lastname: Camarasa
authors.forename: Federico
authors.initials: F
authors.lastname: Gago
authors.forename: María-Luisa
authors.initials: ML
authors.lastname: Jimeno
authors.forename: Ana
authors.initials: A
authors.lastname: San-Félix
mesh_terms: D002236:Carbohydrate Conformation; D002241:Carbohydrates / Q000737:chemistry*; D007202:Indicators and Reagents; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D009705:Nucleosides / Q000138:chemical synthesis* / Q000737:chemistry; D009904:Optical Rotation; D011743:Pyrimidines / Q000737:chemistry*
chemical_list: D002241:Carbohydrates; D007202:Indicators and Reagents; D009705:Nucleosides; D011743:Pyrimidines