Used For Solid-phase Synthesis Of Chemical Synthesis Of Nucleoside Derivatives

Non-natural DNAs have been served as a probe to study the interaction between protein and DNA and DNA’s dynamic properties during the interaction, which now have beome a very popular method in the area of structural biology. However, how can we get these modified nucleotides? The biological method by using enzymes to modify the nucleotides could obtain the needed modified DNAs, but the yield is very low. The appearance of solid-phase synthesis provides us an alternative way. We could modify the nucleotides by protecting the 5’-OH with 4, 4’-dimethoxytrityl group and 3’-OH with 2-cyanoethyl-N,N’-diisopropyl phosphoramide to get the corresponding phosphoramidites, which are further used in the solid-phase synthesis to get the modified DNAs. These phosphoramidites can be modified on either furanose or bases, such as the following two structures:3’-O-(2-Cyanoethyl-N,N’-diisopropylphos-phoramido)-5’-O-(4,4’-dimethoxytrityl)-5-fluoro-2’-deo xyuridine and 3’-O-(2-Cyanoethyl-N,N’-diis-opropylphosphoramido)-5’-(4,4’-dimethoxytrityl)-2’-fluoro-2’-deoxypurine). The introduction of fluorine into the nucleotides makes it possible to obtain a lot of useful inforamtion by 19F-NMR studies. In this dissertation we designed and synthesized three compounds of these three phosphoramidites as follows. Part 1:Spontaneous methylation of DNA by endogenous methylating agents generates a variety of genotoxic adducts, the most prevalent of which is N7-methylguanine (m7G). Apart from its occurrence as a natural lesion, m7G generated via deliberate DNA methylation has seen widespread use as a probe of protein-DNA interactions and as a key component of the Maxam-Gilbert DNA sequencing method, enabled the first experimental determination of gene sequences. Most organisms express DNA glycosylase enzymes that locate m7G residues and excise them (eq 1); the most well-studied of these are E. coli AlkA and human Aag, enzymes that are functionally equivalent but structurally dissimilar. Fluorine substitution at the 2’-position in 2’-deoxy nucleosides is well-known to slow or even abrogate enzymatic catalysis of N-glycosi’dic bond cleavage, presumably via destabilization of the obligate oxocarbenium ion intermediate.6 Since both enzymatic and nonenzymatic depurination of m7G 2’-deoxyriboside (m7dG) proceed through such an intermediate, we reasoned that 2’-fluorination of m7dG would most likely retard both processes, providing a useful means to incorporate the lesion into DNA and study its enzymatic repair.Part 2:TM3 was designed and synthsised for the struchture study of amino transferaseNOTE:TM19-[2-Deoxy-5-O-(4,4’-dimethoxytrityl)-2-fluoro-_-D-arabinofuranosyl]-1,9-dihydro-7-methyl-2-phenoxyacetamido-6H-purin-6-one 3-O-(2-cyanoethyl-N，N-diisiopropyl)] phosphoramiditeTM29-[2-Deoxy-5-O-(4,4’-dimethoxytrityl)-2-fluoro-_-D-arabinofuranosyl]-1,9-dihydro-7-methyl-2-isopropylamido-6H-purin-6-one 3-O-(2-cyanoethyl-N,N-diisiopropyl)] phosphoramiditeTM33’-O-(2-Cyanoethyl-N,N’-diisopropylphosphoramido)-5’-O-(4,4’-dimethoxytrityl)-4--(2,4,6&rimethylphenyl)-2’-deoxyuridine...