Use of the Dithiasuccinoyl (Dts) Amino Protecting Group for Solid-Phase Synthesis of Protected Peptide Nucleic Acid (PNA) Oligomers<sup>1-3</sup>
作者:Marta Planas、Eduard Bardají、Knud J. Jensen、George Barany
DOI:10.1021/jo9824394
日期:1999.10.1
"Peptide nucleic acid" (PNA) oligomers replace the oligonucleotide backbone of DNA with an achiral and neutral poly[N-(2-aminoethyl)glycine] backbone, and the four-natural nucleobases are attached through methylene carbonyl linkages to the glycine nitrogens. The present work describes the efficient conversion of N-omega-Boc/side-chain Z-protected PNA monomers to the corresponding derivatives protected by the thiolyzable N-omega-dithiasuccinoyl (Dts) function. After acidolytic removal of Boc, treatment with bis(ethoxythiocarbonyl) sulfide gave the N-omega-ethoxythiocarbonyl (Etc) derivatives, which were silylated at the alpha-carboxyl and converted to the heterocycle by reaction with (chlorocarbonyl)sulfenyl chloride. Net yields of homogeneous monomers were 71-78%. Conditions in the solid-phase mode for thiolytic removal of the Dts group, and for coupling of protected monomers, have been studied extensively and optimized. A protocol featuring (i); Dts removal with dithiothreitol (DTT) (0.5 M) in acetic acid (HOAc) (0.5 M)-CH2Cl2 (2 + 8 min) (ii) short neutralization with N,N-diisopropylethylamine (DIEA)-CH2Cl2 (1:19, 1 + 2 min); and (iii) coupling mediated by HBTU-DIEA (3:1) in N-methyl-2-pyrrolidinone (NMP) (3 h) pas applied to the solid-phase synthesis of Dts-T-4-Gly-NH2, Dts-G(Z)-G(Z)-T-A(Z)-Gly-NH2, Dts-A(Z)-T-C(Z)-G(Z)-Gly-NH2, and Dts-G(Z)-C (Z)-A(Z)-T-Gly-NH2. The indicated protected PNA derivatives were released from the support, and their structures were verified by mass spectrometry.
"肽核酸"(PNA)寡聚体将DNA的寡核苷酸骨架替换为无手性且中性的聚[N-(2-氨基乙基)甘氨酸]骨架,并通过甲基 carbonyl 连接物将四个天然碱基连接到甘氨酸氮上。本研究描述了将N-omega-Boc/侧链Z保护的PNA单体高效转化为相应受硫化N-omega-二硫琥珀酰基(Dts)保护的衍生物。在酸性条件下去除Boc后,使用双(乙氧基 carbonyl)硫化物处理得到N-omega-乙氧基 carbonyl(Etc)衍生物,这些衍生物在 alpha-carboxyl 上被硅化,并与(chlorocarbonyl)sulfenyl chloride反应生成杂环。纯品单体的净收率为71-78%。固相模式下Dts基团的硫醇化去除条件,以及受保护单体的偶联条件,已得到广泛研究和优化。一种包含以下步骤的方案被用于固相合成:(i) 使用二硫苏糖醇(DTT)(0.5 M)在醋酸(HOAc)(0.5 M)-CH2Cl2(2 + 8分钟)中去除Dts;(ii) 使用N,N-二异丙基乙胺(DIEA)-CH2Cl2(1:19, 1 + 2分钟)进行短时间中和;(iii) 使用HBTU-DIEA(3:1)在N-甲基-2-吡咯烷酮(NMP)中进行3小时的偶联。该方案应用于Dts-T-4-Gly-NH2、Dts-G(Z)-G(Z)-T-A(Z)-Gly-NH2、Dts-A(Z)-T-C(Z)-G(Z)-Gly-NH2和Dts-G(Z)-C(Z)-A(Z)-T-Gly-NH2的固相合成。所述受保护的PNA衍生物从载体上分离,并通过质谱法验证了其结构。