An alternative method for the synthesis of 2′-halogeno-1′,2′-unsaturated uridine derivatives through <i>syn</i>-elimination of pivalic acid of 2′-halogeno- 2′-deoxy-1′-pivaloyloxyuracil nucleoside: preparation of its 2′-<i>C</i>-branched nucleosides
Abstract An alternative method for the preparation of 2′-bromo- (5b) and 2′-iodo- (5c) 1′,2′-unsaturated uracil nucleosides has been developed. The protocol was on the basis of the syn-elimination of pivalic acid from 2′-bromo-(7a,b) and 2′-iodo-(9a,b) 1′-pivaloyloxy-2′-deoxyuridine derivatives, which were derived from the halo-pivaloyloxylation of 3′,5′-bis-O-TBDMS-1′,2′-unsaturated uridine 1. Compounds
5-<i>Exo</i> versus 6-<i>Endo</i> Cyclization of Nucleoside 2-Sila-5-hexenyl Radicals: Reaction of 6-(Bromomethyl)dimethylsilyl 1‘,2‘-Unsaturated Uridines
作者:Junko Ogamino、Hideaki Mizunuma、Hiroki Kumamoto、Shingo Takeda、Kazuhiro Haraguchi、Kazuo T. Nakamura、Hiroshi Sugiyama、Hiromichi Tanaka
DOI:10.1021/jo040260p
日期:2005.3.1
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
We report that TBDMS-protected 1-(2-deoxy-D-erythro-pent-1-enofuranosyl)-6-(tributyl-stannyl)uracil, when treated with LDA or LTMP, undergoes an anionic stannyl migration to yield the 2′-stannylated product. Optimization of the reaction conditions has disclosed an efficient entry to compounds variously substituted at the 2′-position. Desilylation of these compounds caused no further elimination, and