5-Exo versus 6-endo cyclization of nucleoside 2-sila-5-hexenyl radicals: reaction of 6-(bromomethyl)dimethylsilyl 1',2'-unsaturated uridines.
The mode of cyclization of 2-sila-5-hexen-1-yl radicals generated from 6-(bromomethyl)dimethylsilyl-1',2'-unsaturated uridines was investigated. In contrast to the case of the 2'-unsubstituted 6-silicon-tethered substrate (4), which undergoes exclusive 6-endo-cyclization, reactions of the 2'-substituted (Me, CO2Me, OBz, and Cl) derivatives (14, 20, 22, and 24) uniformly proceeded in preferential or exclusive 5-exo-mode. The Tamao oxidation of the resulting cyclized products was also carried out to synthesize the corresponding 1'-C-hydroxymethyl derivatives.
Ogamino
Junko
J
School of Pharmaceutical Sciences, Showa University, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo 142-8555, Japan.
Mizunuma
Hideaki
H
Kumamoto
Hiroki
H
Takeda
Shingo
S
Haraguchi
Kazuhiro
K
Nakamura
Kazuo T
KT
Sugiyama
Hiroshi
H
Tanaka
Hiromichi
H
D003500:Cyclization; D005609:Free Radicals / Q000737:chemistry; D008968:Molecular Conformation; D009705:Nucleosides / Q000138:chemical synthesis / Q000737:chemistry*; D017646:Organosilicon Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D014529:Uridine / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry*
D005609:Free Radicals; D009705:Nucleosides; D017646:Organosilicon Compounds; D014529:Uridine