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-anhydro intermediate are no longer
applicable because of the absence of 2-exo-oxygen on purine rings.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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