Synthesis and NMR assignment of pentacycloundecane precursors of potential pharmaceutical agents

Abstract

The synthesis and complete NMR elucidation of eight novel pentacycloundecane (PCU) derivatives are reported. These compounds are precursors in the synthesis of PCU-based anti-tuberculosis (TB) agents and potential human immunodeficiency virus (HIV) protease inhibitors. Two-dimensional (2D) NMR techniques were used to assign the NMR spectra for these compounds. Substitution of the cage molecule at (C-8/11) further complicates the assignment, since some of the substituted alkyl chain groups overlap with the cage proton signals. The side chain heteroatoms also introduce a rare through-space deshielding effect to some of the carbon atoms of the cage skeleton. Ring strain in the rigid cage skeleton appears to induce drastic electronic changes in some parts of the cage framework. This observation is more dramatic for the C-4 methylene group of the cage diols and the cage ethers.

Synthesis and Antioxidant Investigation of Ag₂S Nanoparticles Obtained from Silver(I) Complex of <i>N</i>-Methyl<i>-N</i>-Phenyl- Dithiocarbamate

“…In the carbon-13 NMR spectrum, the signal at 204.85 ppm was the resonant frequency of the quaternary carbon. The presence of the heteroatoms around this characteristic signal was responsible for greater deshielding, thereby resulting in the appearance of the peak significantly downfield [25]. The resonant signals of the phenyl group were identified at 126.92, 128.72, 129.42, 130.09, and 146.31 ppm [26].…”

NMR elucidation of novel SQ109 derivatives

“…NMR and computational study of 'cage' molecules such as pentacycloundecane and trishomocubane based compounds has been a major focus of our group for the past 5 years [25][26][27][28][29][30][31][32][33][34][35][36]. We recently reported the NMR elucidation of pentacycloundecane based tetraamines [37,38] which were screened for their anti-tuberculosis activities [39].…”

Preparation and complete 1 H and 13C assignment of some pentacyclo[5.4.0.02,6.03,10.05,9]undecane‐8,11‐dione (PCUD) derivatives

“…These pentacyclic structures have been incorporated into many molecules capable of antifungal and antibacterial activity, HIV protease inhibition and anti‐inflammatory activity . As a direct result of their importance, research on PCUD derivatives continues to the present day . However, although the NMR data for this class of compound is reported extensively in the general synthetic literature, in many cases, a detailed assignment of the data is missing.…”