Ethylthio-17-tetrazole

The reaction with 4-nitrophenol activated by 5-ethylthio-l-ff-tetrazole led to formation of the 4-nitrophenyl phosphite (step a). Among several boronating reagents tested borane-dimethyl sulfide gave the optimal yield of... 

Shaw has reported the first syntheses of thymidine- and 2 -deoxy-5-fluorouridine - 3, 5 - cyclic boranophosphorothioate (103a,b). These analogues, displaying increased lipophilicity, were prepared from a key intermediate, a cyclic phosphoramidite obtained by heating a thoroughly degassed HMPA solution of the nucleoside. This phosphoramidite was then converted to a cyclic phosphite triester in the presence of 4-nitrophenol and 5-ethylthio-lH-tetrazole, and converted to the boranated complex in situ. The cyclic boranophosphite was then converted to the 3, 5 -cyclic boranophosphorothioate. ... 

Shaw reported the synthesis of P-tyrosinyl-(P-0)-5-P-nucleosidyl boranophos-phates (190a,b) obtained in a one-pot synthetic procedure via a phosphoramidite and that of the nucleoside 3, 5 -cyclic boranophosphorothioates (191a,b) prepared from a cyclophosphoramidite intermediate. The cyclophosphoramidite, obtained by heating the nucleoside with HMPA was transformed to the phosphite triester by reaction with 4-nitrophenol in the presence of 5-ethylthio-l//-tetrazole. The boranophosphite was oxidized with Li2S after boronation with BH3.SMe2. 

The use of a high-loaded polystyrene (HLP) support has been described for the large scale synthesis of RNA. Biologically active ribozyme sequences were synthesised on a 200 pmol scale using this support in conjunction with 2 -0-tert-butyldimethylsilyl monomers and 5-ethylthio-l/f-tetrazole as the activating agent. 

With modified nucleotides, above all those bearing bulky substituents at 2 -position (most important the 2 -t-butyl(dimethyl)silyl-protection in ORN-synthesis), a tendency for lower coupling yields is observed. Improvement of 1//-tetrazole amidite activation has been achieved by use of 5-(4-nitrophenyl)- and 5-ethylthio-l //-tetrazole with their lower pKa values and compounds with increased nucleophilicity, such as 4,5-dicyanoimidazoles (Table 3). 

Ancillary reagents 3% TCA in methylene chloride (ABI) cap B 16% A-methyl imidazole in THE (ABI) cap A 10% acetic anhydride/ 10% 2,6-lutidine in THE (ABI) 16.9 mM I2, 49 mM pyridine, 9% water in THE (Perseptive) Burdick Jackson (Muskegon, MI) synthesis grade acetonitrile. A choice of 5-ethylthio-l-A-tetrazole solution (0.25 M in acetonitrile), prepared from the solid obtained from American International Chemical (Matick, MA), or 1-A-tetrazole... 

A-Phenylimidazolium trillate A-Methylbenzimidazolium trillate Benzimidazolium triflate A-Phenylimidazolium perchlorate Imidazolium perchlorate A-Acetylphenylimidazolium triflate Pyridinium tetrafluoroborate 4,5-Dicyanoimidazole 2-Bromo-4,5-dicyanoimidazole 5-(Ethylthio)-1 //-tetrazole... 

Introduction. Tetrazoles have widespread applications in medicinal chemistry as well as in energetic materials. 5-Alkylthlotetrazoles, especially 5-ethylthio-l//-tetrazole (1), serve as powerful activators in DNA and RNA syntheses. The title compound Is a better activator than the corresponding 5-alkyl or 5-aryltetrazoles due to the presence of the alkylthio group which renders the tetrazole more acidic. 1 is considerably more soluble In acetonitrile than simple alkyltetrazoles, and the higher concentration results In a better activator performance. ... 

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