Cyclobutanes

Cyclobutane motifs are often introduced when a lead series needs a compact saturated ring that can lock substituent orientation more tightly than larger carbocycles. Their strain and small size make them useful for adding three-dimensional shape without adding much bulk, which is why medicinal chemists frequently explore them as conformationally restrictive bioisosteres. These building blocks are particularly valuable in lead optimization, strained-ring analogue design, and scaffold refinement.