Synthesis of ¹⁵N-Labeled Bevirimat Derivatives as Isotopic Chemical Probes of HIV-1 Maturation Inhibition

Characterizing protein-drug interactions at the atomic level is challenging partly because small molecules can be difficult to detect within large biomolecular complexes. We have developed a strategy to introduce NMR-active isotopic ¹⁵N labels into derivatives of bevirimat (BVM), a triterpenoid inhibitor of HIV-1 maturation. Isotopically labeled compounds were synthesized through concise and efficient routes using commercially available, isotopically enriched building blocks. Three ¹⁵N-labeled BVM derivatives were prepared to be used as molecular probes to investigate HIV-1 protein interactions. These labeled compounds enable site-specific ¹⁵N detection of the inhibitor in both solution and solid-state NMR experiments, which will be useful to obtain molecular-level insight into the interactions between BVM derivatives and its target HIV-1 Gag protein. Synthetic incorporation of NMR-active isotopes produces chemical probes for atomic-level analysis of next-generation HIV-1 therapeutics derived from BVM and can be applied to other derivatives of betulinic acid with various medical applications.