Cycloleucine

Cycloleucine is a non-proteinogenic amino acid. It could be classified as a cyclic derivate of norleucine, having two hydrogen atoms less. Leading structure is a cyclopentane-ring. The α-carbon atom is not a stereocenter.

Cycloleucine is a non-metabolisable amino acid and is a specific and reversible inhibitor of nucleic acid methylation, and as such is widely used in biochemical experiments.