ξ-

{
  "id": "MLC-T-CHM-012730",
  "term": "ξ-",
  "field": "Chemistry",
  "definition": "A Greek letter prefix (xi) used in chemical nomenclature to denote an unknown or undefined stereochemical configuration at a specific chiral center in a molecule. When the absolute or relative configuration of a stereocenter has not been determined, the ξ prefix is placed before the locant of that center. This symbol is frequently used in the context of amino acids and peptides when the configuration (D or L) of a particular residue is unassigned.",
  "synonyms": [
    "xi-"
  ],
  "subject": "Chemical Nomenclature and Structure Representation",
  "see_also": [
    "chiral"
  ],
  "references": [
    "PAC, 1984, 56, 595. 'Nomenclature and Symbolism for Amino Acids and Peptides' on page 601 (https://doi.org/10.1351/pac198456050595)"
  ],
  "url": "https://mlchart.com/terminology/chemistry/x-term/"
}