From the methanol extract of the aerial parts of Peperomia blanda (Piperaceae), two chromenes were isolated and characterized mainly through application of 2D-NMR spectroscopy. The structures were 2S-(4-methyl-3-pentenyl)-6-formyl-8-hydroxy-2,7-dimethyl-2H-chromene and 2S-(4-methyl-3-pentenyl)-5-hydroxy-6-formyl-2,7-dimethyl-2H-chromene named as blandachromenes I and II, respectively.

Four N-(4-halophen-yl)-4-oxo-4H-chromene-3-carboxamides (halo = F, Cl, Br and I), N-(4-fluoro-phen-yl)-4-oxo-4H-chromene-3-carboxamide, C16H10FNO3, N-(4-chloro-phen-yl)-4-oxo-4H-chromene-3-carboxamide, C16H10ClNO3, N-(4-bromo-phen-yl)-4-oxo-4H-chromene-3-carboxamide, C16H10BrNO3, N-(4-iodo-phen-yl)-4-oxo-4H-chromene-3-carboxamide, C16H10INO3, have been structurally characterized. The mol-ecules...

In the title compound, C(16)H(9)BrO(5)·2C(3)H(7)NO, the chromene ring system is essentially planar. The two dimethyl-formamide solvent mol-ecules are linked by inter-molecular O-H⋯O hydrogen bonds to the 6-bromo-3-hydr-oxy-4-oxo-2-phenyl-4H-chromene-8-carboxylic acid molecules.

In the crystal structure of the title compound, C(15)H(9)FO(3), inversely oriented mol-ecules form inversion dimers through pairs of O-H⋯O hydrogen bonds. The benzene ring is twisted at an angle of 12.0 (1)° relative to the 4H-chromene skeleton of the mol-ecule. Adjacent 4H-chromene units are parallel in a given column or oriented at an angle of 50.0 (1)° in neighboring, inversely oriented, col...

In the title compound, C16H12O4, the substituent benzene ring and meth-oxy group are twisted relative to the 4H-chromene skeleton by 24.1 (1) and 61.3 (1)°, respectively. In the crystal, mol-ecules are connected by classical O-H⋯O and weak C-H⋯O hydrogen bonds, forming chains parallel to [201]. The 4H-chromene ring systems of adjacent mol-ecules are either parallel or inclined at an angle of 28...

In the title compound, C13H12Cl N O2S2, the 2H-chromene ring system is almost planar, with a maximum deviation of 0.005 (2) Å. The packing features C-H⋯S hydrogen bonds and π-π inter-actions between fused benzene rings of chromene [shortest centroid-centroid distances = 3.6553 (13) and 3.5551 (13) Å].

The aerial parts of Tephrosia carrollii afforded two chromene chalcones. Their structures and stereochemistry were established by spectroscopic methods. The structure of oaxacacin was revised and confirmed by X-ray diffraction. In this paper, we describe the isolation of the chalcone known as "oaxacacin" and the new chalcone named epoxyobovatachalcone. The compound der. oaxacacin was found to b...

In the title compound, C19H22N2O4, the six-membered cyclo-hexenone ring of the chromene unit adopts an envelope conformation, with the dimethyl-substituted C atom as the flap, while the pyran ring has a boat conformation. These two mean planes are inclined to one another by 6.65 (13)°·The benzene ring is normal to the 4H-chromene moiety mean plane, making a dihedral angle of 89.18 (5)°. The met...

A new chromene derivative, 2-(4',8'-dimethylnona-3'E,7'-dienyl)-8-hydroxy-2,6-dimethyl-2H-chromene (1) together with four known natural products, methylfarnesylquinone (2), isololiolide (3), pheophytin a (4), and β-carotene (5) were isolated from the brown alga Homoeostrichus formosana. The structure of 1 was determined by extensive 1D and 2D spectroscopic analyses. Acetylation of 1 yielded the...

In the title compound, C(15)H(10)O(4), the benzene ring is twisted at an angle of 20.7 (1)° relative to the 4H-chromene skeleton. In the crystal, adjacent mol-ecules are linked via a network of O-H⋯O and C-H⋯O hydrogen bonds. The mean planes of adjacent 4H-chromene moieties are parallel or oriented at an angle of 20.9 (1)° in the crystal structure.