Várnagy Erzsébet, Tóth Gergő, Hosztafi Sándor, Dobó Máté, Fejős Ida, Béni Szabolcs
Department of Pharmacognosy, Semmelweis University, Üllői út 26, H-1085 Budapest, Hungary.
Center for Pharmacology and Drug Research & Development, Semmelweis University, Üllői út 26, H-1085 Budapest, Hungary.
Molecules. 2025 Feb 28;30(5):1125. doi: 10.3390/molecules30051125.
The tetrahydroisoquinoline skeleton is a pharmacologically significant core structure containing chiral centers, making enantiomeric separation crucial due to the potentially distinct biological effects of each enantiomer. In this study, laudanosine (-methyl-tetrahydropapaverine) and its three derivatives (6'-bromo-laudanosine, norlaudanosine, and -propyl-norlaudanosine) were synthesized and used as model compounds to investigate chiral recognition mechanisms. Screening over twenty cyclodextrins (CyDs) as chiral selectors in capillary electrophoresis (CE), we found anionic CyDs to be the most effective, with sulfated-γ-CyD (S-γ-CyD) achieving a maximum of 10.5 for laudanosine. Notably, octakis-(6-deoxy-6-(2-carboxyethyl)-thio)-γ-CyD (sugammadex, SGX), heptakis-(2,3--diacetyl-6--sulfo)-β-CD (HDAS), heptakis-(2,3--dimethyl-6--sulfo)-β-CD (HDMS), and octakis-(2,3--dimethyl-6--sulfo)-γ-CD (ODMS) provided excellent enantioseparation for all four analytes. Following HPLC screening on CyD-based and polysaccharide-based chiral stationary phases, semi-preparative HPLC methods using amylose and cellulose-based columns were optimized to isolate enantiomers. The purity of the isolated enantiomers was evaluated by HPLC, and their configurations were confirmed via circular dichroism spectroscopy. The isolated enantiomers allowed us to explore enantiomer migration order reversals in CE and enantiomer elution order reversal in HPLC. Further H and 2D ROESY NMR experiments provided atomic-level insights into enantioselective complex formation, confirming enantiomer differentiation by SGX and elucidating the inclusion complex structure, where the ring C immersion into the CyD cavity is prevalent.
四氢异喹啉骨架是一种具有药理学意义的核心结构，含有手性中心，由于每种对映体可能具有不同的生物学效应，因此对映体分离至关重要。在本研究中，合成了劳丹诺辛（-甲基-四氢罂粟碱）及其三种衍生物（6'-溴-劳丹诺辛、去甲劳丹诺辛和-丙基-去甲劳丹诺辛），并将其用作模型化合物来研究手性识别机制。在毛细管电泳（CE）中筛选了二十多种环糊精（CyDs）作为手性选择剂，我们发现阴离子型CyDs最为有效，硫酸化-γ-CyD（S-γ-CyD）对劳丹诺辛的分离度最高可达10.5。值得注意的是，八（6-脱氧-6-（2-羧乙基）-硫代）-γ-CyD（舒更葡糖，SGX）、七（2,3-二乙酰基-6-磺基）-β-环糊精（HDAS）、七（2,3-二甲基-6-磺基）-β-环糊精（HDMS）和八（2,3-二甲基-6-磺基）-γ-环糊精（ODMS）对所有四种分析物都提供了出色的对映体分离。在基于环糊精和多糖的手性固定相上进行高效液相色谱（HPLC）筛选后，优化了使用直链淀粉和纤维素基柱的半制备HPLC方法以分离对映体。通过HPLC评估分离出的对映体的纯度，并通过圆二色光谱确认其构型。分离出的对映体使我们能够探索CE中对映体迁移顺序的反转以及HPLC中对映体洗脱顺序的反转。进一步的1H和二维旋转坐标系相关光谱（2D ROESY NMR）实验提供了对映选择性复合物形成的原子水平见解，证实了SGX对对映体的区分并阐明了包合物结构，其中环C浸入CyD腔中很普遍。
