title: Single crystal X-ray structures of the two 4-heptadecyl derivatives of (1R,5S)-3,6,8-trioxabicyclo[3.2.1]octane.
abstract: The single crystal structures of the two diastereomeric 4-heptadecyl derivatives of (1R,5S)-3,6,8-trioxabicyclo[3.2.1]octane have been determined by X-ray diffraction to be (1R,4R,5S)-heptadecyl-3,6,8-trioxabicyclo[3.2.1]octane (I) and (1R,4S,5S)-4-heptadecyl[3,6,8-trioxabicyclo[3.2.1]octane (II), respectively, which have an exo or axial 4-heptadecyl group, and an endo or equatorial 4-heptadecyl group, respectively. The structures of I and II had been suggested by their phase-sensitive 2D NOESY 1H-NMR spectra, but are now established unambiguously. These optically pure non-ionic lipid-like amphipathic molecules (I and II) represent the first 3,6,8-trioxabicyclo[3.2.1]octanes for which single crystal structures have been solved. Crystals of both isomer I and isomer II were orthorhombic with space group P2(1)2(1)2(1), and had unit cell dimensions of a = 9.586, b = 43.14, c = 5.289 A, and a = 7.34, b = 51.8, c = 5.636 A, respectively. The structures of I and II were both solved by using direct methods to R = 0.045 and R = 0.086, respectively. Both I and II pack in stacked bilayers with interdigitating and tilting hydrocarbon chains. The molecular and hydrocarbon cross sections are I: S = 50.70 A2, sigma = 19.00 A2; and II: S = 41.37 A2, sigma = 18.26 A2.
authors.affiliation: Department of Radiology, University of Connecticut Health Center, Farmington 06030, USA.
authors.forename: J
authors.initials: J
authors.lastname: Moring
authors.forename: R I
authors.initials: RI
authors.lastname: Duclos
authors.forename: J H
authors.initials: JH
authors.lastname: Zhang
authors.forename: L G
authors.initials: LG
authors.lastname: Herbette
authors.forename: X
authors.initials: X
authors.lastname: Xie
authors.forename: A
authors.initials: A
authors.lastname: Makriyannis
mesh_terms: D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000737:chemistry*; D018360:Crystallography, X-Ray; D008051:Lipid Bilayers / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008968:Molecular Conformation
chemical_list: D019086:Bridged Bicyclo Compounds, Heterocyclic; D008051:Lipid Bilayers; C096481:4-heptadecyl-3,6,8-trioxabicyclo(3.2.1)octane