The leucines are primarily the four isomeric amino acids: leucine, isoleucine, tert-leucine (terleucine, pseudoleucine) and norleucine. Being compared with the four butanols, they could be classified as butyl-substituted glycines; they represent all four possible variations. Leucine and isoleucine belong to the proteinogenic amino acids; the others are non-natural.

Isomers

Including the stereoisomers, six further isomers could be added: D -leucine, D -isoleucine, L -alloisoleucine, D -alloisoleucine, D -tert-leucine and D -norleucine.

Derivatives

Cycloleucine could be classified as a cyclic derivative of norleucine. With a cyclopentane-ring, it has two hydrogen atoms fewer and thus is not an isomer. The α-carbon atom is not a stereocenter.

Literature