T. V. Sreevidya

Synthesis and characterization of some chalcones and their cyclohexenone derivatives

A series of chalcones and their derivatives have been synthesized. Chalcones, 1-(1,3-benzodioxol-5-yl)-3-(aryl)-prop-2-en-1-ones were prepared by the aldol condensation of 1-(1,3-benzodioxol-5-yl)ethanones and aryl aldehydes. Based-catalyzed condensation of 1-(1,3-benzodioxol-5-yl)-3-(aryl)prop-2-en-1-ones with ethyl acetoacetate yields corresponding ethyl 4-(1,3-benzodioxol-5-yl)-6-(aryl)-2-oxocyclohex-3-ene-1-carboxylates. Some of the synthesized chalcones were reported in the literature; the newly synthesized compounds were characterized by single crystal X-ray studies, IR, 1H-NMR and LCMS mass spectral analysis.

Redetermination of dihydro­artemisinin at 103 (2) K

Tthe structure of the title compound, C15H24O5, has been redetermined at 103 (2) K, with much improved precision. The title compound was first reported by Luo, Yeh, Brossi, Flippen-Anderson & Gillardi [Helv. Chim. Acta (1984). 67, 1515–1522]. It is a derivative of the antimalaria compound artemisinin and consists primarily of three substituted ring systems fused together. A cyclohexane ring (with a distorted chair conformation), is fused to a tetrahydropyran group (also with a distorted chair conformation), and is adjacent to an oxacycloheptane unit containing an endoperoxide bridge. This gives the molecule a unique three-dimensional arrangement. The crystal packing is stabilized by intermolecular C–H⋯O and O–H⋯O interactions between an H atom from the cyclohexane ring and an O atom from the endoperoxide bridge, as well as between the hydroxyl H atom and an O atom from a tetrahydropyran ring.

A second polymorph of β-arteether

The crystal structure of the title compound, C17H28O5, reported here is a polymorph of the structure first reported by El-Feraly, Al-Yahya, Orabi, McPhail & McPhail [J. Nat. Prod. (1992). 55, 878–883]. It is a derivative of the antimalaria compound artemisinin and consists primarily of three substituted ring systems fused together. A cyclohexane ring (distorted chair conformation) fused to a tetrahydropyran group (distorted chair) is adjacent to an oxacycloheptane unit containing an endo-peroxide bridge, giving the molecule its particular three-dimensional arrangement. The crystal packing is stabilized by intermolecular C—H⋯O interactions between an O atom from the endo-peroxide bridge and H atoms from both the cyclohexane and seven-membered oxacycloheptane fused rings, as well as between an O atom and H atom from adjacent tetrahydropyran rings. The two polymorphs have the same space group and similar cell parameters for the a and b axes, but significantly different values for the c axis.

4-Chloro-8-(trifluoromethyl)quinoline

The title compound, C10H5ClF3N, crystallizes with two almost identical molecules in the asymmetric unit. Geometric parameters are in the usual ranges. The crystal packing is characterized by C-H center dot center dot center dot N weak hydrogen bonds and pi-pi stacking interactions.

(E)-1-(1,3-Benzodioxol-5-yl)-3-(3-bromo­phen­yl)prop-2-en-1-one

In the title compound, C16H11BrO3, the molecules adopt an E configuration with respect to the C=C double bond of the propenone unit. The 13 non-H atoms of the benzodioxole and propenone units are approximately coplanar (r.m.s. deviation = 0.027 Å) and the bromobenzene ring plane forms a dihedral angle of 10.8 (1)° to this plane. The structure is layered, with the molecules forming a herring-bone arrangement within each layer.

Redetermination of α- D -glucosamine hydrochloride: elucidation of the hydrogen-bonding scheme

The previously reported crystal structures Chu & Jeffery (1965). Proc. R. Soc. London Ser. A, 285, 470 - 479; Chandrasekharan & Mallikarjunan (1969). Z. Kristallogr. 129, 29] of the title compound, C6H14NO5+ center dot Cl-, have been confirmed to higher precision, and the H atoms located, allowing the elucidaton of the hydrogen- bonding network. A combination of O - H center dot center dot center dot O, N - H center dot center dot center dot O, O - H center dot center dot center dot Cl and N - H center dot center dot center dot Cl links results in a three- dimensional network. Considered by themselves, the inter- cation O - H O and N - H center dot center dot center dot O hydrogen bonds result in undulating (001) layers. The configurations of the chiral C atoms are: C1 S, C2 R, C3 R, C4 S and C5 R.

(2E)-3-(4-Butoxy­phen­yl)-1-(4-chloro­phen­yl)prop-2-en-1-one

The central double bond in the title molecule, C19H19ClO2, is trans configured. Geometric parameters are in normal ranges.

(2E)-1-(4-Bromophenyl)-3-(4-nitrophenyl)- prop-2-en-1-one

In the approximately planar molecule of the title compound, C15H10BrNO3, the dihedral angle between the two benzene rings is 4.97 (18)degrees. Intermolecular C-H center dot center dot center dot O interactions help to form chains of molecules in the crystal structure.