Bicyclo[1.1.1]pentane

Bicyclo[1.1.1]pentane has rapidly established itself as one of the most compelling sp³-rich scaffolds in contemporary medicinal chemistry. Bicyclo[1.1.1]pentane has emerged over the past decade as a valuable three-dimensional bioisostere for benzene, attracting considerable interest in pharmaceutical research for its ability to improve drug-like properties. The Bicyclo[1.1.1]pentane motif has emerged within drug discovery as a valuable bioisostere for internal alkynes, tert-butyl groups, and monosubstituted or 1,4-disubstituted arenes, with its appeal originating from its ability to add three-dimensional character and saturation to compounds. The 1,3-bridgehead positions project substituents in a linear orientation that closely mirrors the geometry of a para-disubstituted benzene ring, preserving the pharmacophoric exit vectors of the parent aromatic whilst replacing a flat, metabolically labile core with a fully saturated cage. This bioisosteric replacement can improve physicochemical properties including better solubility, lower lipophilicity, and higher metabolic stability, and is also used to access novel intellectual property space.

The pivotal demonstration of Bicyclo[1.1.1]pentane's utility came in 2012, when Stepan and colleagues at Pfizer replaced the central fluorophenyl ring of the γ-secretase inhibitor avagacestat with a Bicyclo[1.1.1]pentane unit. The modified compound not only exhibited equivalent biological activity to the parent drug but also displayed enhanced solubility, membrane permeability, and reduced metabolic susceptibility, translating into excellent oral absorption characteristics in a mouse model of γ-secretase inhibition. Since then, more than 300 patents have described BCP-containing compounds in drug discovery, with contributions from major pharmaceutical organisations spanning neuroscience, cardiovascular medicine, and immuno-oncology. Synthetic access to the scaffold, historically dependent on volatile [1.1.1]propellane, has expanded considerably through photoredox catalysis, strain-release chemistry from bicyclo[1.1.0]butane, and flow chemistry approaches, collectively transforming Bicyclo[1.1.1]pentane from a laboratory curiosity into a practically accessible building block.

Our range of Bicyclo[1.1.1]pentanes features novel substitutions and the incorporation of synthetically tractable functional groups such as boronic acids and esters, amines, carboxylic acids, ketones, hydroxyls and halogens to enable expedient synthetic strategies.

Please examine a selection of Bicyclo[1.1.1]pentanes in our catalogue. The full range can be found using the substructure feature of our Search tools.