title: XRD and VCD: a marriage of love or convenience? Honeymoon around a cyclic urea derivative.
abstract: The structures and absolute configurations of the enantiomers (3aR,8aR)-2,2-dimethyl-4,4,8,8-tetraphenyl-4,5,6,7,8,8a-hexahydro-3aH-1,3-dioxolo[4,5-e][1,3]diazepin-6-one 0.33-hydrate, C(32)H(30)N(2)O(3)·0.33H(2)O, (Ia), and (3aS,8aS)-2,2-dimethyl-4,4,8,8-tetraphenyl-4,5,6,7,8,8a-hexahydro-3aH-1,3-dioxolo[4,5-e][1,3]diazepin-6-one 0.39-hydrate, C(32)H(30)N(2)O(3)·0.39H(2)O, (Ib), have been elucidated unambiguously using the complementary power of single-crystal X-ray diffraction (XRD) and vibrational circular dichroism (VCD). The enantiomers crystallize in the Sohncke space group P2(1)2(1)2 and pack as dimers stabilized by two symmetric hydrogen bonds involving one amide group each of the cyclic urea moiety. This double interaction is capped by a water molecule that partially occupies a site lying on the twofold axis and forms an uncommon hydrogen bond between the two monomers. A comparison between the solid-state VCD characterizations and the Bayesian statistics on Bijvoet differences determined from the XRD measurements reveals a tendency towards the correct determination of the absolute configuration by this latter method.
authors: C. D. Nenitzescu Center of Organic Chemistry, Romanian Academy, Spl. Independentei 202 B, 060023 Bucharest, Romania.
authors: Dragos
authors: D
authors: Gherase
authors: Jean-Valère
authors: JV
authors: Naubron
authors: Christian
authors: C
authors: Roussel
authors: Michel
authors: M
authors: Giorgi
mesh_terms: D001381:Azepines / Q000737:chemistry*; D002942:Circular Dichroism; D018360:Crystallography, X-Ray; D004149:Dioxoles / Q000737:chemistry*; D006860:Hydrogen Bonding; D008958:Models, Molecular; D013237:Stereoisomerism; D014508:Urea / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: C575795:(3aR,8aR)-2,2-dimethyl-4,4,8,8-tetraphenyl-4,5,6,7,8,8a-hexahydro-3aH-1,3-dioxolo(4,5-e)(1,3)diazepin-6-one; D001381:Azepines; D004149:Dioxoles; D014508:Urea