Biomedical Engineering Reference
In-Depth Information
Scheme 3.3 Synthesis of 2 0 -Se-derivatized cytidine phosphoramidite, DNAs, and RNAs.
( a )R 1 : TMS-Im, then POCl 3 , 1H-1, 2, 4-triazole, Et 3 NinCH 3 CN; R 2 :2,4,6-
triisopropylbenzenesulfonyl chloride, Et 3 N, DMAP in CH 2 Cl 2 .( b ) Aqueous NH 4 OH. ( c ) TMS-Im,
then Ac 2 O, TEA, and DMAP in THF. ( d ) 2-Cyanoethyl N,N-diisopropylchlorophosphoramidite,
N,N-diisopropylethylamine in CH 2 Cl 2. ( e ) Solid-phase synthesis
modification was successfully incorporated into DNAs and RNAs (tRNA T
Chair-
pin loop) with high yields. The structure of 2 0 -SeMe-T-containing DNA (5 0 -G T 2 0 Se
GTACAC-3 0 ) 2 was determined at 1.4 A resolution (Fig. 3.3 ), and it is virtually
identical to native structure. Moreover, the thermal denaturing experiment also
suggested the 2 0 -Se-T-modified DNAs and RNAs have almost the same denaturing
temperature as the corresponding native ones.
Synthesis and Crystallography Application of 2 0 -Se-Purine
3.2.2.2
Encouraged by the successful synthesis and structure study of DNAs and RNAs
containing 2 0 -Se-pyrimidines, 2 0 -Se-purine analogs started attracting researchers'
interest. For the synthesis of 2 0 -Se-purine nucleosides, the conventional methods
for 2 0 -Se-pyrimidine synthesis involving 2, 2 0 -anhydro intermediate are no longer
applicable because of the absence of 2-exo-oxygen on purine rings. In order
to overcome this obstacle, Micura's lab developed a new synthetic strategy by
converting 2 0 -OH group on arabinosyl nucleoside to a good leaving group then
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