49 research outputs found
(E,E)-1,2-Bis(2,4,5-trimethoxybenzylidene)hydrazine
The asymmetric unit of the title compound, C20H24N2O6, contains one half-molecule, the complete molecule being generated by a crystallographic inversion centre. The molecule is nearly planar with a dihedral angle between the two benzene rings of 0.03 (4)° and the central C/N/N/C plane making a dihedral angle of 8.59 (7)° with each of its two adjacent benzene rings. The two methoxy groups at the ortho and meta positions are slightly twisted [C—O—C—C torsion angles = 7.23 (12) and 5.73 (13)°], whereas the methoxy group at the para position is almost coplanar with the attached benzene ring [C—O—C—C torsion angle = −2.02 (13)°]. The crystal structure is stabilized by a weak C—H⋯π interaction
(E)-N′-(3-Ethoxy-4-hydroxybenzylidene)-4-methoxybenzohydrazide
In the molecule of the title benzohydrazide derivative, C17H18N2O4, the dihedral angle between the benzene rings is 6.86 (11)°. The methoxy group of the 4-methoxyphenyl fragment deviates slightly [Cmethyl—O—C—C = 10.0 (4)°] with respect to the benzene ring, whereas the ethoxy group of the 3-ethoxy-4-hydroxyphenyl fragment is is almost coplanar [C—O—C—Cmethyl = 178.5 (2)°]. In the crystal, molecules are linked by N—H⋯O, O—H⋯O and C—H⋯O hydrogen bonds into a two-dimensional network parallel to the ab plane. C—H⋯π interactions and C⋯O [2.980 (3) Å] short contacts are also observed
Redetermination and absolute configuration of pruniflorone M monohydrate
The title xanthone known as pruniflorone M (systematic name: (2R)-5,10-dihydroxy-2-hydroxymethyl-1,1-dimethyl-1H-furo[2,3-c]xanthen-6-one), crystallized in a monohydrate form, C18H16O6·H2O. It was isolated from the green fruits of Cratoxylum formosum ssp. pruniflorum. The structure of the title compound has been reported previously [Boonnak et al. (2010 ▶). Aust. J. Chem. 63, 1550–1556], but we report here the absolute configuration determined using Cu Kα radiation. There are two crystallograpically independent molecules in the asymmetric unit, which differ slightly in the bond angles. The hydroxymethyl substituents at position 2 of the furan rings of both pruniflorone M molecules adopt R configurations. In both molecules, the three rings of the xanthone skeleton are approximately coplanar, with an r.m.s. deviation of 0.0124 (2) Å for one molecule and 0.0289 (2) Å for the other, and the furan ring adopts an envelope conformation. In the crystal, molecules of pruniflorone M and water are linked into a two-dimensional network by O—H⋯O hydrogen bonds and weak C—H⋯O interactions. The crystal structure is further consolidated by π–π interactions with centroid–centroid distances in the range 3.5987 (13)–3.7498 (14) Å. Short C⋯C [3.378 (3) Å] and O⋯O [2.918 (3) Å] contacts are also observed
Redetermination and absolute configuration of 7α-hydroxyroyleanone
The title compound [systematic name: 7α,12-dihydroxy-8,12-abietadiene,11,14-dione or (4bS,8aS,10R)-3,10-dihydroxy-2-isopropyl-4b,8,8-trimethyl-1,4,4b,5,6,7,8,8a,9,10-decahydrophenanthrene-1,4-dione], C20H28O4, is an abietane diterpenoid, which was isolated from the roots of Premna obtusifolia (Verbenaceae). Its crystal structure has been reported previously [Chen et al. (2000 ▶). Jiegou Huaxue, 19, 122–125], but the absolute configuration could not be determined using data collected with Mo radiation. This redetermination using Cu radiation shows the the absolute configurations of the stereogenic centres at positions 4b, 8a and 10 to be S, S and R, respectively. Two intramolecular O—H⋯O hydrogen bonds [one generating an S(5) ring and one generating an S(6) ring] and a number of short C—H⋯O contacts occur. In the crystal, molecules are linked into infinite chains propagating in [100] by O—H⋯O hydrogen bonds and weak C—H⋯O interactions
Vieillardiixanthone B1
The title compound [systematic name: 1,5-dihydroxy-3,6-dimethoxy-4-(2-methylbut-3-en-2-yl)-9H-xanthen-9-one], C20H20O6, is a xanthone, which was isolated from the roots of Cratoxylum formosum ssp. pruniflorum. The three rings in the molecule are approximately coplanar, with an r.m.s. deviation of 0.0372 (2) Å for the plane through the 14 non-H atoms. The O atoms of the two hydroxy substituents also lie close to this plane with deviations of 0.0669 (2) and 0.1122 (2) Å, respectively. The 1,1-dimethyl-2-propenyl substituent is in a (−)-anticlinal conformation. Intramolecular O—H⋯O hydrogen bonds generate S(5) and S(6) ring motifs. In the crystal, molecules are linked into infinite chains along [010] by O—H⋯O hydrogen bonds and weak C—H⋯O interactions. π–π interactions with centroid–centroid distances of 3.6172 (10) and 3.6815 (10) Å are also observed
Absolute configuration of isovouacapenol C
The title compound, C27H34O5 {systematic name: (4aR,5R,6R,6aS,7R,11aS,11bR)-4a,6-dihydroxy-4,4,7,11b-tetramethyl-1,2,3,4,4a,5,6,6a,7,11,11a,11b-dodecahydrophenanthro[3,2-b]furan-5-yl benzoate}, is a cassane furanoditerpene, which was isolated from the roots of Caesalpinia pulcherrima. The three cyclohexane rings are trans fused: two of these are in chair conformations with the third in a twisted half-chair conformation, whereas the furan ring is almost planar (r.m.s. deviation = 0.003 Å). An intramolecular C—H⋯O interaction generates an S(6) ring. The absolute configurations of the stereogenic centres at positions 4a, 5, 6, 6a, 7, 11a and 11b are R, R, R, S, R, S and R, respectively. In the crystal, molecules are linked into infinite chains along [010] by O—H⋯O hydrogen bonds. C⋯O [3.306 (2)–3.347 (2) Å] short contacts and C—H⋯π interactions also occur
Absolute configuration of vouacapen-5α-ol
The title compound, C20H30O2, {systematic name: (4aR,6aS,7R,11aS,11bR)-4,4,7,11b-tetramethyl-1,2,3,4,4a,5,6,6a,7,11,11a,11b-dodecahydrophenanthro[3,2-b]furan-4a-ol}, is a cassane furanoditerpene which was isolated from the roots of Caesalpinia pulcherrima. The absolute configurations at positions 4a, 6a, 7, 11a and 11b are R, S, R, S and R, respectively. The molecule has four-fused rings consisting of three cyclohexane rings and one furan ring. The three cyclohexane rings are trans-fused. Two cyclohexane rings are in chair conformations, while the third is in an envelope conformation. In the crystal structure, the molecules are linked by intermolecular O—H⋯O hydrogen bonds into a zigzag chain along the a axis. A short O⋯O contact [3.0398 (14) Å] is also present
(E)-1-(2-Furyl)-3-(2,4,6-trimethoxyphenyl)prop-2-en-1-one
In the title heteroaryl chalcone derivative, C16H16O5, the dihedral angle between the furan and benzene rings is 14.45 (6)°. The three methoxy groups are almost coplanar with their attached benzene ring [C—C—O—C torsion angles = 2.07 (17), −5.04 (17) and 2.85 (16)°]. An intramolecular C—H⋯O hydrogen bond occurs. In the crystal, adjacent molecules are linked into X-shaped chains along the c axis by weak C—H⋯O(enone) interactions. These chains are stacked along the b axis. C⋯O [3.3308 (13)–3.4123 (14) Å] short contacts are also observed
ent-(15S)-Pimar-8(14)-ene-15,16-diol
The title compound {systematic name: (S)-1-[(2S,4aR,8aR)-2,4b,8,8-tetramethyl-2,3,4,4a,4b,5,6,7,8,8a,9,10-dodecahydrophenanthren-2-yl]ethane-1,2-diol}, C20H34O2, is an ent-pimarane diterpenoid which was isolated from the stem bark of Ceriops tagal. In the asymmetric unit, there are two crystallographically independent molecules, which are conformationally almost identical. In each molecule, the two cyclohexane rings of the fused three-ring system adopt chair conformations, while the cyclohexene ring is in an envelope conformation, with the methylene C atom next to the side chain as the flap atom. In the crystal, molecules are stacked in columns along the b axis through O—H⋯O hydrogen bonds