24小时热门版块排行榜

返回列表

当前主题已经存档。

superdujb

金虫 (初入文坛)

应助: 0 (幼儿园)
金币: 556
散金: 90
帖子: 39
在线: 59.6小时
虫号: 752393
注册: 2009-04-19
专业: 波谱分析与成像分析

[交流] 【求助】+【有效期到9月2日】【翻译段落】

The Huisgen-Meldal-Sharpless ‘click’ reaction has emerged as
a convenient and effective approach for the preparation of a
diversity of new molecules with various functionalities performed
under simple reaction conditions. The reaction is orthogonal to
most of the common biomolecule substituents and chemoselective
under Cu(I) catalysis.1 Thus, the protocol is particularly attractive
to be applied in drug design,2 molecular diagnostics3,4 polymer
synthesis, material science,5–10 and other areas of chemistry and
chemical biology.11–13
Recently, we reported on the synthesis of oligonucleotides
incorporating 7-deaza-7-(octa-1,7-diynyl)-2'-deoxyguanosine (1)
(purine numbering is used in the results and discussion section).
The side chains bearing terminal triple bonds were conjugated
with various azides including the dye 3-azido-7-hydroxycoumarin
by the Huisgen-Meldal-Sharpless ‘click’ reaction.11c,14 Spectro-
scopic studies showed that the ﬂuorescence is strongly quenched
when the DNA nucleobase belongs to the class of pyrrolo[2,3-

d]pyrimdines. An electron transfer from the nucleobase to the
dye moiety was suggested.14 Thus, it was anticipated that other
nucleobases having different redox potentials may not show such
drawback. Pyrazolo[3,4-d]pyrimidine nucleosides offer properties
which make them applicable as alternative systems.15 They show
similar base pairing characteristics and can be functionalized at
the 7-position. 8-Aza-7-deazapurine (pyrazolo[3,4-d]pyrimidine)
nucleosides have already been incorporated into DNA including
7-propynyl and 7-halogeno derivatives.16–18 It was shown that
the 8-aza-7-deaza-2'-deoxyguanosine residues 2a–c form stable
base pairs with dC giving steric freedom to 7-substituents to
be well accommodated in the major groove of duplex DNA.18
Usually, 7-substituted nucleosides form more stable duplexes than
the non-functionalized ones.18–22 Thus, pyrazolo[3,4-d]pyrimidine
nucleosides can be considered as purine nucleoside shape mimics
which will not disturb the DNA duplex structure.
This manuscript reports on the synthesis of 8-aza-7-deaza-
7-(octa-1,7-diynyl)-2 '-deoxyguanosine (2d), its conversion into
the phosphoramidite building blocks (3a,b) and their ap-
plication in solid-phase oligonucleotide synthesis (Fig. 1).
Studies  regarding  base pairing and  ﬂuorescence  properties
were carried out on  oligonucleotides  incorporating  nucleo-
side 2d.  The azide-alkyne ‘click’ reaction  for  the dye con-
jugation  with 3-azido-7-hydroxycoumarin on nucleosides  and
oligonucleotides  with  side chains having terminal triple bonds
was  studied  according to Scheme 1. Fluorescence enhance-
ment  of  the oligonucleotide  coumarin dye conjugates is ex-
pected for oligonucleotides containing pyrazolo[3,4-d]pyrimidine
dye  conjugates  compared to  pyrrolo[2,3-d]pyrimidine deriva-
tives.

回复此楼