Pyta Krystian, Przybylski Piotr, Bartl Franz
Faculty of Chemistry, Adam Mickiewicz University, Umultowska 89b, 61-614 Poznan (Poland).
Chemphyschem. 2015 Apr 7;16(5):938-42. doi: 10.1002/cphc.201402892. Epub 2015 Jan 29.
Water-mediated proton transfer in six new derivatives of 3-formylrifamycin SV that contain crown, aza-crown, and benzo-crown ether rings were investigated by FTIR and NMR spectroscopy. (1)H-(1)H COSY couplings provide evidence for the formation of zwitterionic structures of the aza-crown and crown ether derivatives of rifamycin, in which a proton from one of the phenolic groups is transferred to tertiary and secondary nitrogen atoms. The increased intensity of the continuous absorption in the mid-infrared region together with the NMR data indicate proton transfer from the phenol group of the rifamycin core to the cavity of the benzo-crown ether ring. This proton transfer is achieved by formation of hydronium (H3O(+)) or Zundel ions (H5O2(+)), which form intermolecular hydrogen bonds with the oxygen atoms of the crown ether. DFT calculations are in agreement with the spectroscopic data and allow visualization of the structures of all new rifamycin derivatives, characterized by different intramolecular protonation sites.
通过傅里叶变换红外光谱（FTIR）和核磁共振光谱（NMR）研究了含有冠醚、氮杂冠醚和苯并冠醚环的六种新型3-甲酰基利福霉素SV衍生物中的水介导质子转移。¹H-¹H COSY耦合为利福霉素的氮杂冠醚和冠醚衍生物形成两性离子结构提供了证据，其中来自一个酚羟基的质子转移到叔氮原子和仲氮原子上。中红外区域连续吸收强度的增加以及核磁共振数据表明质子从利福霉素核心的酚羟基转移到苯并冠醚环的腔内。这种质子转移是通过形成水合氢离子（H₃O⁺）或祖德尔离子（H₅O₂⁺）来实现的，它们与冠醚的氧原子形成分子间氢键。密度泛函理论（DFT）计算与光谱数据一致，并能够可视化所有新型利福霉素衍生物的结构，其特征在于不同的分子内质子化位点。
