Synthesis and NMR assignment of pentacycloundecane precursors of potential pharmaceutical agents

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. Copyright © 2010 John Wiley & Sons, Ltd. The synthesis and complete NMR elucidation of eight novel pentacycloundecane (PCU) precursors of PCU based anti‐tuberculosis (TB) agents and potential HIV protease inhibitors are reported. The side chain heteroatoms also introduce 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 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.