Synthesis of meta-substituted arene bioisosteres from [3.1.1]propellane

Small-ring cage hydrocarbons are common bioisosteres for para-substituted benzene rings in drug design, exhibiting superior pharmacokinetic properties compared to the parent aromatics. In contrast, scaffolds mimicking meta-substituted arenes are lacking due to the challenge of synthesising saturated isosteres that accurately reproduce the substituent vectors of the corresponding arene. Here we report the use of [3.1.1]propellane as a convenient and scalable precursor to bicyclo[3.1.1]heptanes (BCHeps), hydrocarbons whose bridgehead substituents map precisely onto the geometry of meta-substituted benzenes. This precursor undergoes a range of radical-based transformations to generate medicinally-relevant carbon- and heteroatom-substituted BCHeps, including BCHep pharmaceutical analogues. Comparison of ADME properties of the latter reveals improved metabolic stability relative to their parent drugs, validating the potential of this meta-arene analogue as an sp3-rich motif in drug design.