Department of Chemistry, University of Turku, 20014 Turku, Finland.
Molecules. 2021 Jan 18;26(2):490. doi: 10.3390/molecules26020490.
Oligonucleotides modified by a 2'-deoxy-2'-(-methoxyamino) ribonucleotide react readily with aldehydes in slightly acidic conditions to yield the corresponding -(methoxy)oxazolidine-linked oligonucleotide-conjugates. The reaction is reversible and dynamic in slightly acidic conditions, while the products are virtually stable above pH 7, where the reaction is in a ''switched off-state''. Small molecular examinations have demonstrated that aldehyde constituents affect the cleavage rate of the -(methoxy)oxazolidine-linkage. This can be utilized to adjust the stability of this pH-responsive cleavable linker for drug delivery applications. In the present study, Fmoc-β-Ala-H was immobilized to a serine-modified ChemMatrix resin and used for the automated assembly of two peptidealdehydes and one aldehyde-modified peptide nucleic acid (PNA). In addition, a triantennary -acetyl-d-galactosamine-cluster with a β-Ala-H unit has been synthesized. These aldehydes were conjugated via (methoxy)oxazolidine-linkage to therapeutically relevant oligonucleotide phosphorothioates and one DNA-aptamer in 19-47% isolated yields. The cleavage rates of the conjugates were studied in slightly acidic conditions. In addition to the diverse set of conjugates synthesized, these experiments and a comparison to published data demonstrate that the simple conversion of Gly-H to β-Ala-H residue resulted in a faster cleavage of the -(methoxy)oxazolidine-linker at pH 5, being comparable (T ca 7 h) to hydrazone-based structures.
经 2'-脱氧-2'-(-甲氧基氨基)核糖核苷酸修饰的寡核苷酸在微酸性条件下与醛反应迅速，生成相应的-(甲氧基)恶唑啉键连的寡核苷酸缀合物。该反应在微酸性条件下是可逆和动态的，而在 pH 7 以上时产物几乎稳定，此时反应处于“关闭状态”。小分子研究表明，醛成分会影响-(甲氧基)恶唑啉键的裂解速率。这可用于调节用于药物输送应用的这种 pH 响应性可裂解接头的稳定性。在本研究中，Fmoc-β-Ala-H 固定在丝氨酸修饰的 ChemMatrix 树脂上，并用于自动组装两种肽醛和一种醛修饰的肽核酸 (PNA)。此外，还合成了具有β-Ala-H 单元的三触角乙酰-d-半乳糖胺簇。这些醛通过（甲氧基）恶唑啉键与治疗相关的寡核苷酸硫代磷酸酯和一个 DNA-适体以 19-47%的分离收率缀合。在微酸性条件下研究了缀合物的裂解速率。除了合成的各种缀合物外，这些实验以及与已发表数据的比较表明，将 Gly-H 简单转化为β-Ala-H 残基会导致在 pH 5 时-(甲氧基)恶唑啉键更快地裂解，与腙基结构相当（T ca 7 h）。
