- Incorporation of methylated pyrimidine analogues into RNA
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Routes for the preparation of 2'-silyl protected phosphoramidites of the modified nucleosides O2-methyluridine and O4-methyluridine are described. Methodology for the site-specific incorporation of these phosphonamidetes into a 25 nucleotide long oligoribonucleotide sequence by solid-phase synthesis is reported.
- Vyle, Joseph S.,Young, Karen J.,Grasby, Jane A.
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p. 5093 - 5096
(2007/10/03)
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- Synthesis of Uridine Analogues to Probe the Functional Group Requirements of the Hairpin Ribozyme
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O4-Methyluridine, O2-methyluridine and 4Huridine phosphoramidites were prepared with 2'-O-silyl protection.The methyl modified pyrimidines were synthesised from uridine via the triazolide (O4-methyl) or 2,5'-cyclo derivative (O2-methyl).An improved synthesis of protected 4-thiouridine was also performed.
- Vyle, Joseph S.,Young, Karen J.,Jones, Sarah,Grasby, Jane A.
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p. S280 - S282
(2007/10/03)
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- Nucleosides. Part LIX. The 2-(4-nitrophenyl)ethylsulfonyl (Npes) group: A new type of protection in nucleoside chemistry
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The 2-(4-nitrophenyl)ethylsulfonyl (npes) group is developed as a new sugar OH-blocking group in the ribonucleoside series. Its cleavage can be performed in a β-eliminating process under aprotic conditions using 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) as the most effective base. Since sulfonates do not show acyl migration, partial protection of 1,2-cis-diol moieties is possible leading to new types of oligonucleotide building blocks. A series of Markiewicz-protected ribonucleosides 1-10 is converted into their 2'-O-[2-(4-nitrophenyl)ethylsulfonyl] derivatives 29-38 in which the 5'-O-Si bond can be cleaved by acid hydrolysis forming 39-45. Subsequent monomethoxytritylation leads to 46-50, and desilylation affords the 5'-O-(monomethoxytrityl)-2'-O-[2-(4-nitrophenyl)ethylsulfonyl]ribonucl eosides 51-55. Acid treatment to remove trityl groups do also not harm the npes group(→ 56-58). Unambiguous syntheses of fully blocked 2'-O-[2-(4-nitrophenyl)ethylsulfonyl]ribonucleosides 96-102 are achieved from the corresponding 3'-O-(tert-butyl)dimethylsilyl derivatives. Furthermore, various base-protected 5'-O-(monomethoxytrityl)- and 5'-O-(dimethoxytrityl)ribonucleosides, i.e. 59-77, are treated directly with 2-(4-nitrophenyl)ethylsulfonyl chloride forming in all cases a mixture of the 2',3'-di-O- and the two possible 2'- and 3'-O-monosulfonates 107-148 which can be separated into the pure components by chromatographic methods. The npes group is more labile towards DBU cleavage than the corresponding base-protecting 2-(4-nitrophenyl)ethyl (npe) and 2-(4-nitrophenyl)ethoxycarbonyl (npeoc) groups allowing selective deblocking which is of great synthetic potential.
- Pfister,Schirmeister,Mohr,Farkas,Stengele,Reiner,Dunkel,Gokhale,Charubala,Pfleiderer
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p. 1705 - 1737
(2007/10/02)
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