On the relationships between molecular conformations and intermolecular contacts toward crystal self-assembly of mono-, di-, tri-, and tetra-oxygenated xanthone derivatives

Abstract

Oxygenated xanthones have been extensively investigated over the years, but there are few reports concerning their crystal structure. Our chemical investigations of Brazilian plants resulted in the isolation of four natural products named 1-hydroxyxanthone (I), 1-hydroxy-7-methoxyxanthone (II), 1,5-dihydroxy-3-methoxyxanthone (III), and 1,7-dihydroxy-3,8-dimethoxyxanthone (IV). The structures of these compounds were established on the basis of single crystal X-ray diffraction. The xanthone nucleus conformation is essentially planar with the substituents adopting the orientations less sterically hindered. In addition, classical intermolecular hydrogen bonds (O-HÁÁÁO) present in III and IV give rise to infinite ribbons. However, the xanthone I does not present any intermolecular hydrogen bonds, meanwhile the xanthone II presents only a non-classical one (C-HÁÁÁO). The crystal packing of all xanthone structures is also stabilized by p-p interactions. The fingerprint plots, derived from the Hirshfeld surfaces, exhibited significant features of each crystal structures.

Experimental and theoretical investigation of molecular structure and conformation of the 4-isopropylthioxanthone

“…The least squares planes of the rings A and C form a dihedral angle of 2.55(6)°, those of the rings B and C form an angle of 1.98(6)°, and those of the A and B rings form an angle of 4.40(7)°. As observed and studied previously, the chromene central ring is the most susceptible to distortion [28].…”

“…As observed, this interaction plays an important role in stabilizing the conformation of the isopropyl group thus justifying the slight deviation related to the theoretical calculation results. Also, a common kind of interaction occurring in resonant threefused rings [28] can be seen in Fig. 3b.…”

“…The CÁ Á ÁH contacts account for 14.5% of the Hirshfeld surface, a slightly larger value compared with that of CÁ Á ÁC (12.3%). These three kinds of contacts emphasize the significant occurrence of van der Waals and p-p interactions [28]. Accordingly, the hydrophilic OÁ Á ÁH contact contributions to the crystal structure is 9%.…”

Interplay of thermochemistry and Structural Chemistry, the journal (volume 21, 2010) and the discipline

“…Corrêa et al [149] managed to isolate 1-hydroxyxanthone, 1-hydroxy-7-methoxyxanthone, 1,5-dihydroxy-3-methoxyxanthone, and 1,7-dihydroxy-3,8-dimethoxyxanthone, to determined their X-ray crystal structures and study molecular interactions. Important bonding is represented by hydrogen bonds and the crystal self-assemblies are kept together by p-p interactions.…”

Analgesic and Anti-Inflammatory Activities of the 2,8-Dihydroxy-1,6-Dimethoxyxanthone from Haploclathra paniculata (Mart) Benth (Guttiferae)

“…3,4 Xanthones have been reported to have numerous biological properties, including the antithrombotic and anticancer effects, 5 protein kinase C inhibitor activity, 6 antihypertensive and vasodilatory effects, 7 endothelial cell protective effects, 8 anti-inflammatory, 3,5,[9][10][11] analgesic, 10 and antioxidant activities. 4,7 The 2,8-dihydroxy-1,6-dimethoxyxanthone has been isolated from the H. paniculata, 12 Triperospermum chinense, 13 Gentiana kochiana, 14 and Juglans mandshurica 15 genera. This xanthone has been described as an antimycobacterial agent 16 and elicits central inhibition of monoamine oxidase A.…”