Departament de Química Orgànica and IBUB, Facultat de Química, Universitat de Barcelona , Martí i Franquès 1-11, 08028 Barcelona, Spain.
Bioconjug Chem. 2012 Feb 15;23(2):300-7. doi: 10.1021/bc200598g. Epub 2012 Feb 2.
Phosphorothioate diester oligonucleotides proved to be fully compatible with maleimides in the context of two different conjugation reactions: (a) reaction of (5')diene-[phosphorothioate oligonucleotides] with maleimido-containing compounds to afford the Diels-Alder cycloadduct; (b) conjugation of (5')maleimido-[phosphorothioate oligonucleotides] with thiol-containing compounds. No evidence of reaction between phosphorothioate diesters and maleimides was found in any of these processes. Importantly, in the preparation of (5')maleimido-[phosphorothioate oligonucleotides] from [protected maleimido]-[phosphorothioate oligonucleotides], which requires the maleimide to be deprotected by retro-Diels-Alder reaction (heating for 3-4 h in toluene at 90 °C), no addition of phosphorothioate diester to the maleimide was found either. Finally, maleimide-[phosphorothioate monoester] conjugation was also explored for comparison purposes.
(a)双烯-[硫代磷酸寡核苷酸]与含马来酰亚胺的化合物反应，生成 Diels-Alder 环加成产物；(b)含巯基的化合物与 5'-马来酰亚胺-[硫代磷酸寡核苷酸]的偶联。在这些过程中，没有发现硫代磷酸二酯和马来酰亚胺之间发生反应的证据。重要的是，在由[保护的马来酰亚胺]-[硫代磷酸寡核苷酸]制备 5'-马来酰亚胺-[硫代磷酸寡核苷酸]的过程中，马来酰亚胺需要通过逆 Diels-Alder 反应进行脱保护(在 90°C 的甲苯中加热 3-4 小时)，也没有发现硫代磷酸二酯加到马来酰亚胺中。最后，还探索了马来酰亚胺-[硫代磷酸单酯]的偶联反应，以便进行比较。
