Xanthen-9-one

From a mechanistic point of view, 9-snbstitnted xanthenols 586 (prepared from the dianion of xanthen-9-one 585 in situ generated by a DTBB-catalyzed lithiation in THF, and different alkyl halides in 31-93% yield) are of interest due to rearrangements, which occurred under acidic conditions . ... 

Chromone (4 H-1 -benzopyran-4-one) (21) Xanthone (9H-xanthen-9-one) (22) Flavone (2-phenyl-4 W-1 -benzopyran-4-one)... 

Electronic absorption spectra have been recorded for 38 during flash photolysis of 9,9 -bixanthenyl. The spectra are distinguishable from those of the radical arising in photoexcitation of xanthen-9-one. ... 

Ketyl radicals are involved in various chemical reductions of xanthen-9-one reduction to xanthene by lithium in liquid ammonia, reduction via 9,9 -bixanthenyl-9,9 -diol to xanthen-9-ol by zinc in alkaline ethanol. Attempts to attach an electron to xanthene itself to form an anion-radical in DMF led instead to the formation of 71 xanthene is reducible at lower temperatures, but the radical which results is not, of... 

A Study of the effect of temperature on direct and sensitized photolysis of o-propylphenyl azide (373) was carried out Direct photolysis of 373 in z-octane at room temperature gave 2-methyl-2,3-dihydroindole (374) in trace quantities along with several other products. When xanthen-9-one was used as a triplet sensitizer at room temperature, 374 was obtained in 36% yield. When 373 was photolysed directly at 99°, however, 374 was obtained in 49% yield... 

Nitro-2 fluorene (Ej=59 kcal/mole) and Michler s ketone (Et=61 kcal/mole) are efficient sensitizers for poly(vinylcin-namate) and poly (vinylfurylacrylate) (jl). For this reason, we have tested their efficiency in the case of synthesized polymers. Ravve et al. found that xanthene-9 one (E =74 kcal/mole) increa-... 

A series of novel l, 3-dihydroxyxanthone Mannich base derivatives were synthesized, structure elucidated, and evaluated for anticholinesterase activity. Most of the target compounds exhibited moderate to good inhibitory activities with the IC50 values at micromole level concentration against both acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE). Among them, 2 - ((diethylamino )methyl) -1 -hydroxy- 3 - (3 -methylbut-2-enyloxy) -9H-xanthen-9-one showed potent inhibitory activity against AChE and the best inhibitory activity against BuChE. The Mannich base derivatives were likely to bind to the active site (AS) and the peripheral anionic site (PAS) of cholinesterases [169]. 

The formation of the xanthene also offers an explanation for the reports " " " that contact with air must be avoided during the resin s synthesis and curing, if a graphitizable material is to be obtained. Oxidation sensitivity is entirely consistent with a xanthene compound being the key intermediate, since they can be readily oxidized to form a xanthene-9 -one" . 

Chemically xanthones (9H-xanthen-9-ones) are heterocychc compounds with the dibenzo-y-pyrone framework (1, Fig. 1). The xanthone nucleus is mun-bered according to a biosynthetic convention with carbons 1-4 being assigned to acetate-derived ring A and carbons 5-8 to the shikimate-derived ring B. The other carbons are indicated as 4a, 4b, 8a, 8b, 9, and 9a for structure elucidation pmposes [4]. 

Recently, 59 xanthones (= 9H-xanthen-9-ones) of natural or synthetic origin were investigated for their inhibitory activity toward MAO-A and MAO-B. The majority of the compounds demonstrated reversible, time-independent activities, with selectivity toward MAO-A. The most active inhibitor (1,5-dihydroxy-3-methoxyxanthone) had an IC50 of 40 nM. 3D-QSAR studies revealed the importance of an OH substituent in position 1 or 5 instead of a MeO substituent and the contrary is true for position 3, where MeO... 

Bester K, Theobald N (2000) Results of non-target screening of lipophilic organic pollutants in the German Bight V xanthen-9-one. Wat Res 34, 2277-2282. 

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