Efficient and simple protocol employing borohydride systems to design a selective osthol-zirconium (OST-Zr) library from potential natural products

Abstract

“Drug likeness†of a molecule is the prime criterion for a molecule to exhibit the desired pharmaceutical activity. A pharmacophore, which describes molecular features that are necessary for molecular recognition of a ligand by a biological macromolecule, is well altered by the Structure Activity Relationship (SAR) guidelines through Hydrophobic Lipophilic Balance (HLB) demonstrated by the system. The tailoring is best accomplished by organic functional group interconversion on a potent natural product via a variety of synthetic methodologies available to date. Metal borohydrides (MBH₄) in particular are promising compounds as they can potentially serve varying HLB systems. The reagent acts on the substrate to cause reduction, hydroboration, or a combination of both outcomes for the purpose of rearrangement and fragmentation. Indeed, Zr(BH₄)₄ is expected to be more active and selective as a reducing agent compared to NaBH₄. This study aims at evaluating zirconium borohydride (Zr(BH₄)₄) in tetrahydrofuran (THF) as a reducing system to realize a more selective, meaningful and combinatorial osthol (OST) library from potential natural products and attempt to alternate preparation of the same in THF from known metal borohydrides, limiting reduction of the metal center versus metathesis.