(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