Structural characterization of a degradation product of tin ethyl etiopurpurin (SnET2): Comparison of the long-range Heteronuclear correlations detected using conventional GHMBC and IMPEACH-MBC in conjunction with submicro NMR probe technology

摘要

During the terminal heat sterilization of the lipid emulsion final dose formulation of the photodynamic therapeutic (PDT) agent tin ethyl etiopurpurin (SnET2), a new degradant was observed at very low levels. The degradant, which was prone to photo-instability, was isolated by preparative chromatography and subsequently characterized by mass spectrometry and NMR methods. Reproducible parent ion clusters were only observable via negative ion APCI methods. Because of the limited isolate sample, NMR characterization was done using 1.7 min SMIDG (SubMicro Inverse-Detection Gradient) NMR probe technology in conjunction with the accordion-optimized IMPEACH-MBC long-range heteronuclear shift correlation experiment. The "static" 8 Hz optimization of the GHMBC experiment failed to allow the observation of a number of long-range correlations that were of critical importance to the determination of the structure of the impurity. In contrast, all of the correlations required to assemble the structure were obtained from an IMPEACH-MBC experiment optimized for long-range heteronuclear couplings in the range from 2-10 Hz. [References: 21]