title: Modular synthesis of 5-substituted thiophen-2-yl C-2'-deoxyribonucleosides.
abstract: A new modular methodology of preparation of 5-substituted thiophene-2-yl C-nucleosides was developed. A Friedel-Crafts-type of C-glycosidation of 2-bromothiophene with toluoyl-protected methylglycoside 2 gave the desired protected 1beta-(5-bromothiophen-2-yl)-1,2-dideoxyribofuranose 4a in 60%. The key intermediate 4a was then subjected to a series of palladium-catalyzed cross-coupling reactions. The cross-coupling reactions with alkyl organometallics gave beta-(5-alkylthiophen-2-yl)-2-deoxyribonucleosides 4 and 7 in moderate yields accompanied by side-products of reduction. On the other hand, cross-couplings with arylstannanes proceeded smoothly to give a series of beta-(5-arylthiophen-2-yl)-2-deoxyribonucleosides 4 in good yields. Deprotection of toluoylated nucleosides by NaOMe in MeOH and silylated nucleosides by Et 3N.3HF gave a series of free C-nucleosides 6. Alternatively, other types of 5-arylthiophene C-nucleosides 6 were prepared in one step by the aqueous-phase cross-coupling reactions of unprotected 1beta-(5-bromothiophen-2-yl)-1,2-dideoxyribofuranose with boronic acids. Title 5-arylthiophene C-nucleosides 6 exhibit interesting fluorescent properties with emission maxima varying from 339 to 396 nm depending on the aryl group attached.
authors.affiliation: Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Gilead Sciences & IOCB Research Center, Prague 6, Czech Republic.
authors.forename: Jan
authors.initials: J
authors.lastname: Bárta
authors.forename: Radek
authors.initials: R
authors.lastname: Pohl
authors.forename: Blanka
authors.initials: B
authors.lastname: Klepetárová
authors.forename: Nikolaus P
authors.initials: NP
authors.lastname: Ernsting
authors.forename: Michal
authors.initials: M
authors.lastname: Hocek
mesh_terms: D018360:Crystallography, X-Ray; D003853:Deoxyribonucleosides / Q000138:chemical synthesis* / Q000737:chemistry; D008958:Models, Molecular; D015394:Molecular Structure; D013237:Stereoisomerism; D013876:Thiophenes / Q000138:chemical synthesis* / Q000737:chemistry
chemical_list: D003853:Deoxyribonucleosides; D013876:Thiophenes