L-, and DL-
Prefixes to chemical names for compounds that have a centre of asymmetry in the molecule, and which can therefore have two forms (isomers).
Most naturally occurring sugars have the d-conformation; apart from a few microbial proteins and some invertebrate peptides, all the naturally occurring amino acids have the l-configuration. Chemical synthesis yields a mixture of the d- and l-isomers (the racemic mixture), generally shown as dl-. See also R-.
