15N-, 13C- and 1H-NMR Spectroscopy Characterization and Growth Inhibitory Potency of a Combi-Molecule Synthesized by Acetylation of an Unstable Monoalkyltriazene

Abstract

6-(3-Methyltriaz-1-en-1-yl)-1H-benzo[de]isoquinoline-1,3(2H)-dione referred to as EG22 (8a), is an open-chain 3-alkyl-1,2,3-triazene termed “combi-molecule” designed to inhibit poly(adenosine diphosphate ribose) polymerase (PARP) and damage DNA. To delay its hydrolysis, acetylation of N3 was required. Being a monoalkyl-1,2,3-triazene, EG22 could assume two tautomers in solution or lose nitrogen during the reaction, thereby leading to several acetylated compounds. Instead, one compound was observed and to unequivocally assign its structure, we introduced isotopically labeled reagents in its preparation, with the purpose of incorporating 15N at N2 and 13C in the 3-methyl group. The results showed that the 1,2,3-triazene moiety remained intact, as confirmed by 15N-NMR, coupling patterns between the 15N-labeled N2 and the 13C-labeled methyl group. Furthermore, we undertook heteronuclear single quantum coherence (HSQC) and heteronuclear multiple bond correlation (HMBC) experiments that permitted the detection and assignment of all four nitrogens in 6-(3-acetyl-3-methyltriaz-1-en-1-yl)-1H-benzo[de]isoquinoline-1,3(2H)-dione, referred to as ZSM02 (9a), whose structure was further confirmed by X-ray crystallography. The structure showed a remarkable coplanarity between the N-acetyltriazene and the naphtalimide moiety. Thus, we unequivocally assigned 9a as the product of the reaction and compared its growth inhibitory activity with that of its precursor, EG22. ZSM02 exhibited identical growth inhibitory profile as EG22, suggesting that it may be a prodrug of EG22.

Molecular Profiling of Peanut under Raw, Roasting, and Autoclaving Conditions Using High-Resolution Magic Angle Spinning and Solution 1H NMR Spectroscopy

“…As with the analysis of defatted peanut flour, we used the peak of the anomeric protons to assign the presence of sucrose and glucose; small doublets at 5.2 and 4.7 ppm were assigned to the α- and β-anomeric protons of glucose, respectively ( Figure 3 B,C). 2D HSQC NMR experiments of soaked solutions unequivocally confirmed the structure of sucrose, which was much more abundant than glucose under all conditions ( Figure A1 , Figure A2 and Figure A3 ) [ 28 ]. By contrast to defatted peanut flour, no lipids remained in the soaked solution, revealing peaks in the region from 0.5 to 2.5 ppm, which were assigned to aliphatic protons of free amino acids and protein amino-acid side chains.…”