Five new cassane diterpenes from the seeds and bark of Erythrophleum suaveolens.

Five new cassane-type diterpenoid heterosides, i. e. two cassane-type amides (1-2), two erythrophlamine-type amine esters (3-4) and a non­nitrogenous erythrophlamine analogue (5) were isolated from the root barks (1-2) and the seeds (3-5) of Erythrophleum suaveolens. Their structures were unambiguously established by interpretation of their HRESIMS, 1D and 2D NMR data, and chemical degradation for sugar determination. Compounds 3-5 were evaluated for their cytotoxicity against a panel of three cell lines, revealing modest to strong activities.

Crystal structure, Hirshfeld surface analysis and DFT studies of 2-(2,3-di-hydro-1H-perimidin-2-yl)phenol.

The asymmetric unit of the title compound, C17H14N2O, contains two independent mol-ecules each consisting of perimidine and phenol units. The tricyclic perimidine units contain naphthalene ring systems and non-planar C4N2 rings adopting envelope conformations with the C atoms of the NCN groups hinged by 44.11 (7) and 48.50 (6)° with respect to the best planes of the other five atoms. Intra-molecular O-H⋯N hydrogen bonds may help to consolidate the mol-ecular conformations. The two independent mol-ecules are linked through an N-H⋯O hydrogen bond. The Hirshfeld surface analysis of the crystal structure indicates that the most important contributions for the crystal packing are from H⋯H (52.9%) and H⋯C/C⋯H (39.5%) inter-actions. Hydrogen bonding and van der Waals inter-actions are the dominant inter-actions in the crystal packing. Density functional theory (DFT) optimized structures at the B3LYP/ 6-311 G(d,p) level are compared with the experimentally determined mol-ecular structure in the solid state. The HOMO-LUMO behaviour was elucidated to determine the energy gap.

Crystal structure, Hirshfeld surface analysis and inter-action energy and DFT studies of 2-(2,3-di-hydro-1H-perimidin-2-yl)-6-meth-oxy-phenol.

The title compound, C18H16N2O2, consists of perimidine and meth-oxy-phenol units, where the tricyclic perimidine unit contains a naphthalene ring system and a non-planar C4N2 ring adopting an envelope conformation with the NCN group hinged by 47.44 (7)° with respect to the best plane of the other five atoms. In the crystal, O-HPhnl⋯NPrmdn and N-HPrmdn⋯OPhnl (Phnl = phenol and Prmdn = perimidine) hydrogen bonds link the mol-ecules into infinite chains along the b-axis direction. Weak C-H⋯π inter-actions may further stabilize the crystal structure. The Hirshfeld surface analysis of the crystal structure indicates that the most important contributions for the crystal packing are from H⋯H (49.0%), H⋯C/C⋯H (35.8%) and H⋯O/O⋯H (12.0%) inter-actions. Hydrogen bonding and van der Waals inter-actions are the dominant inter-actions in the crystal packing. Computational chemistry indicates that in the crystal, the O-HPhnl⋯NPrmdn and N-HPrmdn⋯OPhnl hydrogen-bond energies are 58.4 and 38.0 kJ mol-1, respectively. Density functional theory (DFT) optimized structures at the B3LYP/ 6-311 G(d,p) level are compared with the experimentally determined mol-ecular structure in the solid state. The HOMO-LUMO behaviour was elucidated to determine the energy gap.

3-[2-(3-Phenyl-2-oxo-1,2-di-hydro-quin-oxalin-1-yl)eth-yl]-1,3-oxazolidin-2-one.

The di-hydro-quinoxaline ring system of the title mol-ecule, C19H17N3O3, is approximately planar [maximum deviation = 0.050 (2) Å], the dihedral angle between the planes through the two fused rings being 4.75 (8)°. The mean plane through the fused-ring system forms a dihedral angle of 30.72 (5)° with the attached phenyl ring. The mol-ecular conformation is enforced by C-H⋯O hydrogen bonds. In the crystal, mol-ecules are linked by weak C-H⋯O hydrogen bonds, forming a three-dimensional network.

1-Phenyl-3H-2,3-benzodiazepin-4(5H)-one.

The seven-membered ring in the title compound, C(15)H(12)N(2)O, adopts a boat-shaped conformation (with the methyl-ene C atom as the prow and the double-bond C=N pair of atoms as the stern). In the crystal, adjacent mol-ecules are linked by an N-H⋯O hydrogen bond to generate helical chains running along the a axis of the ortho-rhom-bic unit cell.

3-{2-[(3-Phenyl-quinoxalin-2-yl)-oxy]ethyl}-1,3-oxazolidin-2-one.

The asymmetric unit of the title compound, C(19)H(17)N(3)O(3), consists of two independent mol-ecules that are disposed about a pseudo-centre of inversion. The plane of the phenyl substituent is twisted by 38.1 (1)° [43.6 (1)° in the second mol-ecule] out of the plane of the quinoxaline ring system. The five-membered ring of the substituent at the 2-position adopts an envelope conformation; the 5-CH(2) atom representing the flap lies out of the plane defined by the other four atoms [deviation 0.264 (7) Šin the first mol-ecule and 0.291 (6) Šin the second]. The dihedral angle between the five-membered ring and the 4-phenyl ring is 84.9 (1)° while that between the five-membered ring and the 5-phenyl ring is 65.6 (1)°.

3-[2-(3-Methyl-quinoxalin-2-yl-oxy)eth-yl]-1,3-oxazolidin-2-one.

Two isomers were isolated during the reaction between 3-methyl-quinoxalin-2-one and bis-(2-chloro-ethyl)amine hydro-chloride. The crystal structure of one isomer has already been reported [Caleb, Bouhfid, Essassi & El Ammari (2009). Acta Cryst. E65, o2024-o2025], while that of the second isomer is the subject of this work. The title compound, C(14)H(15)N(3)O(3), has a new structure containing oxazolidine and quinoxaline rings linked by an eth-oxy group. The main difference between the two isomers is the position of the oxazolidine group with respect to the quinoxaline system. The dihedral angle between the fused planar rings and the oxazolidin-2-one ring is 41.63 (8)° in the title mol-ecule.