Deracemization
Conversion of a racemic mixture to an enantiopure product without external chiral source.
Context: Strategic for late-stage purification and process intensification.
Example: Viedma ripening, enzymatic deracemization.
Related Terms: Viedma Ripening, Absolute Asymmetric Synthesis.
Reference: Blackmond, Angew. Chem. (2010).
Dextro-(d, +)
Denotes a compound that rotates plane-polarized light to the right (clockwise).
Context: Optical rotation descriptors are experimental and distinct from R/S configuration.
Example: D-(+)-glucose.
Related Terms: Levo-, Optical Activity, Specific Rotation.
Reference: IUPAC Gold Book.
Diastereomer
Stereoisomers not related as mirror images.
Context: Often differ in physical properties, enabling separation and selective synthesis.
Example: Erythro vs threo diols.
Related Terms: Enantiomer, Relative Configuration.
Reference: Eliel & Wilen (1994).
Diastereomeric Excess (de)
Absolute difference between diastereomer fractions.
Context: QC metric when diastereomers are formed.
Example: 80% syn, 20% anti → 60% de.
Related Terms: dr, Stereoselectivity.
Reference: IUPAC Gold Book.
Diastereomeric Ratio (dr)
Ratio of diastereomers formed in a reaction.
Context: Guides optimization of diastereoselective steps.
Example: 95:5 syn:anti aldol product.
Related Terms: Diastereomeric Excess, Stereoselectivity.
Reference: IUPAC Gold Book.
Distomer
The enantiomer with lower or undesirable activity.
Context: May contribute to side effects or be removed in development.
Example: R-citalopram.
Related Terms: Eutomer, Racemate.
Reference: Ariëns (1984).
DNA Chirality
DNA adopts right-handed helices (B-form) with chiral sugar backbone.
Context: Chiral recognition of intercalators and drugs depends on helix sense.
Example: D-sugar backbone in nucleic acids.
Related Terms: Helicity, Stereorecognition.
Reference: Watson & Crick; Voet & Voet (2011).
Double Stereodifferentiation
Outcome determined by interaction of substrate and reagent chirality (matched/mismatched).
Context: Critical in planning complex multi-stereocenter syntheses.
Example: Aldol with chiral enolate and chiral aldehyde.
Related Terms: Matched/Mismatched, Stereocontrol.
Reference: Seebach (1979).
Dynamic Kinetic Asymmetric Transformation (DYKAT)
Asymmetric reaction converting a racemic substrate mixture to a single enantiomer product via equilibration.
Context: Converts racemic starting materials fully to one enantiomer product.
Example: Pd-catalyzed allylic substitutions.
Related Terms: DKR, Enantioconvergent Synthesis.
Reference: Kagan, Acc. Chem. Res. (1997).
Dynamic Kinetic Resolution (DKR)
Resolution combined with in situ racemization to yield >50% of the desired enantiomer.
Context: Boosts efficiency in API synthesis.
Example: Lipase DKR of secondary alcohols.
Related Terms: Kinetic Resolution, DYKAT.
Reference: Pellissier, Tetrahedron (2003).
Dynamic NMR (DNMR)
NMR methods to study exchange processes and barriers (e.g., enantiomerization).
Context: Quantifies ΔG‡ for atropisomer interconversion relevant to stability.
Example: DNMR of hindered biaryls.
Related Terms: Barrier to Rotation, Enantiomerization.
Reference: Sandström, Dynamic NMR (1982).