Shingo Takeda

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Branched sugar nucleosides have attracted much attention due to their biological activities. We have demonstrated that epoxysugar nucleosides serve as versatile precursor for the stereo-defined synthesis of these nucleoside derivatives on the basis of its ring opening with organoaluminum or organosilicon reagents. In this review article, novel methods for(More)
The antiviral drug 2',3'-didehydro-3'-deoxythymidine (D4T; also know as stavudine and Zerit), which is used against human immunodeficiency virus (HIV), causes delayed toxicity (peripheral neuropathy) in long-term use. After examining a series of 2',3'-didehydro-3'-deoxy-4'-substituted thymidine (4'-substituted D4T) analogs, 4'-ethynyl D4T was found to have(More)
Compounds having methyl, vinyl, and ethynyl groups at the 4'-position of stavudine (d4T: 2',3'-didehydro-3'-deoxythymidine) were synthesized. The compounds were assayed for their ability to inhibit the replication of HIV in cell culture. The 4'-ethynyl analogue (15) was found to be more potent and less toxic than the parent compound stavudine.
Lithium hexamethyldisilazide (LiHMDS) can mediate silylation at the 6-position of uridine, although LiHMDS alone is not able to generate the C-6-lithiated uridine. Experimental results showed that temporary silylation of O-4 (or N-3) of the uracil ring triggers the C-6 lithiation with LiHMDS. This finding allowed us to develop an efficient intramolecular(More)
Recently, Grid computing has gathered the attention as a means to efficiently and effectively utilize computational resources among multiple organizations. However, the current Grid technologies do not always provide the computational environment enough to satisfy users' requirements because of the heterogeneity and disconnect among computational resources(More)
Data security is becoming increasingly important as the Grid matures. The advances of the Grid have allowed scientists and researchers to build a data grid where they can share and exchange research-related data and information. In reality, however, these specialists do not benefit enough from this data grid. The reason is that the current Grid does not(More)
A new anti-HIV agent 4'-cyano-2',3'-didehydro-3'-deoxythymidine (9) was synthesized by allylic substitution of the 3',4'-unsaturated nucleoside 14, having a leaving group at the 2'-position, with cyanotrimethylsilane in the presence of SnCl4. Evaluation of the anti-HIV activity of 9 showed that this compound is much less potent than the recently reported(More)
Stereoselective synthesis of 4'-alpha-carbon-substituted nucleosides has been accomplished through epoxidation of 4',5'-unsaturated nucleosides with dimethyldioxirane (DMDO) and successive SnCl(4)-promoted ring opening of the resulting 4',5'-epoxynucleosides with organosilicon reagents. [reaction: see text]
Data security is becoming increasingly important as the Grid matures. The advances of the Grid have allowed scientists and researchers to share and exchange researchrelated data and information. In reality, however, these specialists do not benefit enough on the Grid. The reason is that the current Grid does not have sufficiently robust and flexible data(More)
4',5'-Epoxythymidine (4) was obtained as a single diastereoisomer by oxidation of 3'-O-(t-butyldimethylsilyl)-4',5'-dehydrothymidine (3) with dimethyldioxirane. When the epoxide 4 was treated with allyltrimethylsilane in the presence of SnCl4, regio- (at the C4') and stereoselective (from the alpha-face) cleavage of the oxirane ring proceeded to afford a(More)