Tsujiaki Hata

New guanosine derivatives: facile O6-phosphorylation, thiophosphinylation sulfonylation and silylation of guanosine derivatives by 4-dimethylaminopyridine catalized reaction

Abstract Appropriately protected guanosine derivatives were successfully converted to the corresponding O 6 -substituted guanosine derivatives by treatment with dialkyl- or diaryl-phosphoryl halides, dialkyl- or diaryl-phosphinothioyl halides, arenesulfonyl chlorides, and trialkylsilyl chlorides.

One-step synthesis of 5′-azido-nucleosides

Regioselective azidation of unprotected or appropriately protected nucleosides was conducted by means of the reagent triphenylphosphine–carbon tetrabromide–lithium azide. By use of this reagent, 5′-azido-5′-deoxynucleosides were prepared conveniently in one step from nucleosides in high yields. Secondary hydroxy-groups of appropriately 5′-protected nucleosides were also converted by the reagent to azido-functions with complete inversion.

Diphenylcarbamoyl and propionyl groups: a new combination of protecting groups for the guanine residue

Abstract Protection of the guanine residue with the O 5 -diphenylcarbamoyl and N 2 -propionyl groups is described. These protecting groups could be readily introduced and removed simultaneously. They were used to demonstrate the synthesis of the deoxyguanylate dimer in high yield.

Phthaloyl group : a new amino protecting group of deoxyadenosine in oligonucleotide synthesis

Abstract A phthaloyl group has been introduced into the N 6 -amino group of deoxyadenosine via silylation followed by acylation. The phthaloyl group resulted in remarkable retarding effects on depurination, while it could be removed under milder conditions than the benzoyl group. Thus, a tetradeoxyadenylate has been successfully synthesized in high yield.

Phosphotriester approach to oligothymidylate synthesis utilizing a simple thymidine unit and a new type of condensing agents

Abstract DMTrTp(SPh) 2 was proposed as a simplest “nucleotide unit” for the synthesis of olygothymidylates. One phenylthio group was removed selectively and rapidly from dithiol-esters by 1 M pyridinium hypophosphonate. Two kinds of arenedisulfonyl chlorides were newly prepared and utilized as promising condensing agents.

Synthesis of 5′-alkylthio-5′-deoxynucleosides from nucleosides in a one-pot reaction

5′-Alkyl (aryl) thio-5′-deoxynucleosides [alkyl (aryl) nucleoside sulphides] were prepared in high yields by the reaction of nucleosides with dialkyl or diaryl disulphides in the presence of tri-n-butylphosphine. The method is widely applicable to the synthesis of unsymmetrical sulphides.

A new type of protection mode for the Guanine residue by using 1,2-diisobutyryloxyethylene group

Abstract A new protecting group, 1,2-diisobutyryloxyethylene group, has successfully been used for protection of the guanine residue in the synthesis of oligodeoxyguanylates.

Acylphosphonates : A new method for Stereospecific and Stereoselective Generation of Dideoxyribonucleoside Phosphorothioates via the Acylphosphonate Intermediates

Abstract Dideoxyribonucleoside phosphorothioates were synthesized by a new method via dideoxyribonucleoside 2,2,2-trichloroethoxycarbonylphosphonates and aroylphosphonates. The conversion of dideoxyribonucleoside 2,2,2-trichloroethoxycarbonylphosphonates to dideoxyribonucleoside trimethylsilyl phosphites by treatment with Me3SiCl-Zn-acetylacetone proceeded with retention configuration at phosphorus. The silyl phosphite intermediates were converted to the phosphorothioates by in situ treatment with sulfur. The aroyl groups were easily removed from 8 – 11 by the action of n-BuNH2 and in situ converted to only one diastereomer (Rp-configuration) of dideoxyribonucleoside phosphorothioates by treatment with elemental sulfur.

Acylphosphonates. 5. 1A new method for stereospecific generation of phosphorothioate via aroylphosphonate intermediate

Dideoxynucleoside phosphorothioates were synthesized by a new method via dideoxynucleoside aroylphosphonates. The aroyl groups were easily removed from and 2 by the action of n-BuNH2 and in situ converted to only one diastereomer (Rp-configuration) of dideoxynucleoside phosphorothioates by treatment with elemental sulfur.

Introduction of the 4,4′4′-tris(benzoyloxy)trityl group into the exo amino groups of deoxyribonucleosides and its properties

Abstract The 4,4′,4′-tris(benzoyloxy)trityl (TBTr) group was introduced into the amino groups of the common deoxyribonucleosides by means of the transient protection using the trimethylsilyl group. The TBTr group introduced onto the N6 -amino group of deoxyadenosine was found to have considerable retarding effects on the depurination when treated with acids.