title: Crystal structures of ecdysteroids: the role of solvent molecules in hydrogen bonding and isostructurality.
abstract: Three crystal forms of the steroid 20-hydroxyecdysone were identified by single-crystal X-ray diffraction analysis: a solvent-free modification, a methanol solvate hydrate and a trihydrate. The structure of a closely related steroid, polypodine B (the 5,20-dihydroxy derivative of ecdysone), was determined in its monohydrate form. Since the unit-cell volume of unsolvated 20-hydroxyecdysone was found to be considerably smaller than that of ecdysone [Huber & Hoppe (1965). Chem. Ber. 98, 2403-2424], a new structure determination of ecdysone was performed, which confirmed the unexpected difference between the unit-cell volumes. The crystals of ecdysone and 20-hydroxyecdysone are isostructural, while the mixed solvate of 20-hydroxyecdysone is homostructural with the hydrate of polypodine B. A detailed analysis of the hydrogen-bond networks in these closely related crystal pairs highlights their packing similarities, demonstrates the role of solvent molecules, and explains the unexpectedly small cell volume of 20-hydroxyecdysone.
authors.affiliation: Institute of Chemistry, Chemical Research Center, Hungarian Academy of Sciences, Budapest 114, PO Box 17, H-1525, Hungary.
authors.forename: László
authors.initials: L
authors.lastname: Fábián
authors.forename: Gyula
authors.initials: G
authors.lastname: Argay
authors.forename: Alajos
authors.initials: A
authors.lastname: Kálmán
authors.forename: Mária
authors.initials: M
authors.lastname: Báthori
mesh_terms: D018360:Crystallography, X-Ray; D004441:Ecdysterone / Q000737:chemistry*; D006860:Hydrogen Bonding; D008958:Models, Molecular; D008968:Molecular Conformation; D012997:Solvents / Q000737:chemistry*
chemical_list: D012997:Solvents; D004441:Ecdysterone