A compound may be labeled as dextrorotary by using the "(+)-" or "d-" prefix. Likewise, a levorotary compound may be labeled using the "(−)-" or "l-" prefix. The lowercase "d-" and "l-" prefixes are obsolete, and are distinct from the SMALL CAPS "D-" and "L-" prefixes. The "D-" and "L-" prefixes are used to specify the enantiomer of chiral organic compounds in biochemistry and are based on the compound's absolute configuration relative to (+)-glyceraldehyde, which is the D-form by definition. The prefix used to indicate absolute configuration is not directly related to the (+) or (−) prefix used to indicate optical rotation in the same molecule. For example, nine of the nineteen L-amino acids naturally occurring in proteins are, despite the L- prefix, actually dextrorotary (at a wavelength of 589 nm), and D-fructose is sometimes called "levulose" because it is levorotary.
a compound may be lAbEleD as deXTRorotarY By usiNg the "(+)-" or "D-" preFIx. likEWisE, a LevoRotaRy Compound May bE lABeled usIng thE "(−)-" Or "l-" PRefIx. the loweRcase "d-" aNd "l-" PreFIxes are OBsoLEte, anD are distIncT froM the small caps "D-" And "l-" prefiXeS. the "d-" and "l-" prefIxEs are uSEd tO sPecifY the enanTIomer oF chiraL OrgAnIc compOUnds in bioChemisTRy and ARE BasED on thE cOMpouNd's AbsOLute confIguraTIon RElaTIVe to (+)-glycERaLdehYDE, whIcH iS tHe d-form bY Definition. The pReFix usEd to INdicAtE AbsOlute confIguRaTioN iS Not dIReCtLy rElated to the (+) oR (−) pRefix used TO INdicaTe optical RotaTIon in thE SAme molecule. for exAmPLE, niNe of the ninetEen l-amino Acids nATuralLy oCcURRIng iN prOteins aRE, dESpITe the L- Prefix, actualLY dexTroroTary (aT a wavElENgTh of 589 nm), ANd d-FruCTose iS sOmeTimEs CalleD "leVulOse" beCause it is leVoRotarY.