Abstract:We describe a new class of DNA-like oligomers made exclusively of nonnatural, stable C-nucleosides. The nucleosides comprise four types of nonnatural bases attached to a deoxyribose through an acetylene bond with the -configuration. The artificial DNA forms right-handed duplexes and triplexes with the complementary artificial DNA. The hybridization occurs spontaneously and sequence-selectively, and the resulting duplexes have thermal stabilities very close to those of natural duplexes. The artificial DNA might be applied to a future extracellular genetic system with information storage and amplifiable abilities.
The reaction of 3,5-di-O-benzyl-2-deoxy-d-ribofuranose with various alkynyllithium reagents afforded diastereomeric mixtures of the corresponding ring-opened alkynyldiols. The resulting diastereomeric mixtures were successively treated with Co(2)(CO)(8), a catalytic amount of TfOH, Et(3)N, and iodine in one pot to give alkynyl C-3,5-di-O-benzyl-2-deoxy-beta-d-ribofuranosides with high beta-selectivities. The cobalt-mediated cyclization (intramolecular Nicholas reaction) is reversible; thus, thermodynamically more stable beta-anomers were obtained preferentially. The alkynyl C-deoxyribofuranosides were converted to a variety of C-deoxyribofuranoside derivatives.
Carbohydrates
Carbohydrates U 0500Stereoselective Synthesis of Alkynyl C-2-Deoxy-β-D-ribofuranosides via Intramolecular Nicholas Reaction: A Versatile Building Block for Nonnatural C-Nucleosides. -Furanose (I) and alkynyl lithium or magnesium reagents give separable epimeric mixtures of the corresponding ring-opened alkynyldiols. Even if these mixtures are used in the following intramolecular Nicholas reaction, involving complexation of the alkynyl group with Co 2 (CO) 8 , cyclization in the presence of catalytic amounts of TfOH, and decomplexation by iodine, the resulting alkynyl furanosides are obtained with high β-selectivities. Some conversions of one of these products are reported. -(TAKASE, M.; MORIKAWA, T.; ABE, H.; INOUYE*, M.; Org. Lett. 5 (2003) 5, 625-628; Fac. Pharm. Sci., Toyama Med. Pharm. Univ., Japan Sci. Technol. Corp., Toyama 930, Japan; Eng.) -Klein 29-157 2003 Carbohydrates
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