Nucleoside-Based Diarylethene Photoswitches and Their Facile Incorporation into Photoswitchable DNA
Nucleoside-Based Diarylethene Photoswitches and Their Facile Incorporation into Photoswitchable DNA
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DOI：
10.1002/anie.201209943
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发表时间：
2013-01-01
影响因子：
16.6
通讯作者：
Jaeschke, Andres
中科院分区：
文献类型：
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作者：
Cahova, Hana;Jaeschke, Andres
DNA 结构和功能的人工控制是化学和合成生物学中一个有吸引力的领域，[1] 光是一种强大且方便的触发器：它是非侵入性的，提供高时空分辨率，并提供正交性选项。 DNA 对光有反应性：紫外线诱导的嘧啶核苷环二聚化是一种重要的 DNA 损伤类型，已得到深入研究。 [2]有趣的是，这种化学特性从未被用于构建基于 DNA 的可逆光开关，并且该领域所有已发表的工作都是基于 DNA 与小型自主光活性分子的共价功能化。 [3]不同类别的此类光活性分子已被研究用于 DNA 光调节；[4] 偶氮苯的使用最为频繁，例如用于调节寡核苷酸双链体和三链体的形成以及 DNA 转录。 [5]在这方面研究的其他物质类别包括芳基乙烯基衍生物，[6]螺吡喃，[3a]以及最近的二芳基乙烯。[3a, 7]虽然总是观察到光异构化对核酸性质的一定影响，但这些方法有一个共同的局限性：因为自主光开关附着在DNA上，无论是作为附属物还是替代核苷， 遇到光子时化学键的重排（即光化学反应）严格限于该非核苷部分。最近，我们实验室报道了一种新型二芳基乙烯光开关，其中两个芳基部分之一被核苷取代，即7-脱氮杂-8-甲基脱氧腺苷（方案1）。 [8]这些光开关是通过聚合多步方法合成的，其中取代的环戊烯基硼酸酯通过铃木交叉偶联与受保护的7-碘-8-甲基-7-脱氮脱氧腺苷反应，然后脱保护。在光照射下，这些化合物被发现会发生高效、可逆的电循环重排，并且开关波长可以通过取代基的化学性质进行调节。研究发现，在非质子溶剂中的转换几乎是定量的，并且这些化合物保留了核苷酸的关键特性，例如它们形成沃森-克里克碱基对的能力。不幸的是，人们发现光异构化在水性溶剂中进行效率低，并且所需的合成限制了这些光开关在寡核苷酸上的应用。为了开发直接访问真正的光可切换 DNA 的方法，我们重新考虑了我们的设计方法；与 7-碘-8-甲基-7-脱氮脱氧腺苷相反，5-碘取代的嘧啶核苷 5I-dU 和 5I-dC 代表易于从商业供应商处获得的寡核苷酸修饰，并为不同的交叉偶联反应提供所需的反应性。 [9]这可以允许将碘修饰的寡核苷酸合成后转化为光开关，从而产生方案 1c 中所示的目标化合物。我们注意到，这种设计挑战了二芳基乙烯光电开关的一些常见设计原则：[10]未取代或取代的嘧啶都没有被用作二芳基乙烯光电开关的成分，并且我们的目标化合物仅包含一个（而不是两个）连接到碳原子上的烷基，这些烷基在环化反应中形成新键，这一特征被认为对于二芳基乙烯光开关的可逆性非常重要。 光切换。该设计首先使用 5-iodo- 在核苷水平上进行了测试
The artificial control of DNA structure and function is an attractive field in chemical and synthetic biology,[1] and light is a powerful and convenient trigger: it is non-invasive, provides high spatio-temporal resolution, and offers the option of orthogonality. DNA is reactive to light: the UV-light-induced cyclodimerization of pyrimidine nucleosides is an important type of DNA damage and has been studied intensively.[2] Interestingly, this chemical property has never been exploited for the construction of DNA-based reversible photoswitches, and all published work in this field is based on the covalent functionalization of DNA with small autonomous photoactive molecules.[3] Different classes of such photoactive molecules have been studied for DNA photoregulation;[4] azobenzenes have been used most frequently and were, for example, employed for modulating oligonucleotide duplex and triplex formation and DNA transcription.[5] Other substance classes studied in this context include arylvinyl derivatives,[6] spiropyranes,[3a] and recently also diarylethenes.[3a, 7] While a certain influence of photoisomerization on the properties of the nucleic acid was always observed, these approaches share one common limitation: because an autonomous photoswitch was attached to the DNA, either as an appendage or substituting for nucleosides, the rearrangement of chemical bonds upon encountering a photon (ie, the photochemical reaction) was strictly confined to this non-nucleosidic moiety. Recently, our lab reported a new type of diarylethene photoswitches in which one of the two aryl moieties was replaced by a nucleoside, namely 7-deaza-8-methyldeoxyadenosine (Scheme 1).[8] These photoswitches were synthesized in a convergent multi-step approach in which a substituted cyclopentenyl boronic ester was reacted with protected 7-iodo-8-methyl-7-deazadeoxyadenosine by Suzuki crosscoupling, followed by deprotection. Upon irradiation with light, these compounds were found to undergo a highly efficient, reversible, electrocyclic rearrangement and the switching wavelength could be tuned by the chemical nature of substituents. Switching was found to be near-quantitative in aprotic solvents, and the compounds retained the key properties of nucleotides, such as their capability to form Watson–Crick base-pairs. Unfortunately, the photoisomerization was found to proceed with low efficiency in aqueous solvents, and the demanding synthesis involved limited the application of these photoswitches to oligonucleotides. To develop straight-forward access to truly photoswitchable DNA, we reconsidered our design approach; in contrast to 7-iodo-8-methyl-7-deazadeoxyadenosine, the 5-iodo-substituted pyrimidine nucleosides 5I-dU and 5I-dC represent oligonucleotide modifications readily available from commercial suppliers, and offer the desired reactivity for different cross-coupling reactions.[9] This could allow for the postsynthetic conversion of an iodo-modified oligonucleotide into a photoswitch, leading to the target compounds shown in Scheme 1c. We note that this design challenges some of the common design principles for diarylethene photoswitches:[10] neither unsubstituted nor substituted pyrimidines have ever been applied as components of diarylethene photoswitches, and our target compounds contain just one (rather than two) alkyl groups attached to the carbon atoms that form the new bond in the cyclization reaction, a feature that is thought to be important for the reversibility of photoswitching. This design was first tested on the nucleoside level employing 5-iodo-