Xanthone Studies. IV. Hydroxyl Proton Chemical Shifts in the Structural Investigation of Xanthones.

Xanthones From Cell Cultures of Hypericum Gnidioides Seem.

“…A low field singlet (δ 12.71) represents the 1hydroxy group. 19 The UV, IR, mass and 1 H-NMR spectroscopic data of compound 2 were in accordance with those published for 1,3,7trihydroxyxanthone. 11,21,22 Compound 3 was also a xanthone.…”

“…A low field singlet (δ 12.53) represents the 1-hydroxy group. 19 The UV, IR, mass and 1 H-NMR spectroscopic data of compound 1 were identical with those reported for 1,7dihydroxyxanthone. 11,20 Compound 2 gave a [M + ] peak at m/z 244 in EI-mass spectrum consistent with the molecular formula C 13 H 8 O 5 .…”

Structure Elucidation of Xanthone Derivatives: Studies of Nuclear Magnetic Resonance Spectroscopy

“…In 1976, Arends and Helboe reported a complementary method based on the chemical shifts in DMSO-d 6 of hydroxyl protons of oxygenated xanthones [2]. Contrary to other polyphenolic compounds, the signal of the hydroxyl protons of xanthones was not impaired by a small amount of water (up to 1 % v/v), nor was excessive signal broadening observed upon keeping these solutions for several hours.…”

“…The early 1 H and 13 C NMR studies of xanthone derivatives have been well documented in the 1970s [1][2][3][4][5][6][7]. These 1 H NMR studies were mainly devoted to the structure elucidation of natural derivatives and were based on chemical shifts, which were estimated from electronic and anisotropic effects, and also on spin coupling data for aromatic protons.…”

Naturally occurring pentaoxygenated, hexaoxygenated and dimeric xanthones: a literature survey

“…The structure of the simple oxygenated xanthones have been established mainly From the UV, IR, MS and NMR data of these compounds 13,14,132,148 Xanthones can be detected by their colours in UV light with and without ammonia or by using a general phenolic spray 72 . The UV spectrum varies in a characteristic manner depending , on the oxygenation pattern and with the availability of a considerable; amount of data, assignments can be readily made.…”