Synthesis of 1,2,3,8-Tetraoxygenated Xanthones

Tetraoxygenated naturally occurring xanthones

“…The preparation of nine 1,2,3,8-tetraoxygenated xanthones was proposed by Gil et al (1990) and 1,3,5,6-, 3,4,5,6-, 3,4,6,7-and 2,3,6,7-tetrahydroxyxanthone were synthesized from benzophenone precursors (Sundholm, 1978). The total synthesis of lichen xanthones (Patel and Trivedi, 1983), synthesis of furanoxanthones (Pinto and Polonia, 1974;Patel and Trivedi, 1991), synthesis of new Mammea africana [56] Morus tinctoria [185] Ochrocarpus odoratus [227] Psorospermum febrifugum [4] Symphonia Subelliptenone F (131) Garcinia subelliptica [168] Garcinia dulcis [166] [131] Gerontoxanthone E (141) Cudrania cochinchinensis [62] Caloxanthone B (142) Carapia inophyllum [173] Tovopyrifolin A (143) Tovomita pyrifolium [47,245] 3-Isomangostin (144) Garcinia mangostana [228,305] 3-Isomangostin hydrate (145) Garcinia mangostana [228] -Mangostin (146) Cratoxylum cochinchinense [36] Garcinia mangostana [20,126,228,298] BR-xanthone A (147) Garcinia mangostana [26] Manglexanthone (148) Tovomita mangle [237] Caloxanthone D (149) Calophyllum inophyllum [171] 3,5-Dihydroxy-6,6-dimethylpyrano(2,3:6,7)-6 HH ,6 HHdimethyldihydropyrano(2 HH ,3 HH :1,2)xanthone (150) Rheedia brasiliensis [82] 1-Isomangostin (151) Garcinia mangostana [228] 11-Hydroxy-1-isomangostin (152) Cratoxylum cochinchinense [310] 1-Isomangostin hydrate (153) Garci...…”

DP4-Assisted Structure Elucidation of Isodemethylchodatin, a New Norlichexanthone Derivative Meager in H-Atoms, from the Lichen Parmotrema tsavoense

“…Biosynthetic considerations would not support one of these candidate structures since the occurrence of an oxygenated substituent at either of these positions cannot be rationalized in regards to the polyketide origin of the norlichexanthone scaffold determined so far. A C-4 location instead of C-5 for this moiety would not have been consistent with its carbon resonating at δ C 131.4 as the joint shielding effects from both an ortho and a para-hydroxy groups would have resulted in its shifting in the 126-128 ppm range [33,34,35,36]. NMR data related to unchlorinated xanthones displaying the same substitution pattern than the left-hand cycle could be compared to the determined constitution of 1 .…”

Total Synthesis of Chalaniline B: An Antibiotic Aminoxanthone from Vorinostat-Treated Fungus Chalara sp. 6661

“…Presumably, the steric hindrance present in both coupling partners is responsible for the difficulty of engaging an acylium cation derived from 7 with a phenol 8 . It is noted, however, that Friedel–Crafts acylation of 3,4,5-trimethoxyphenol derivatives with 2,6-dimethoxybenzoic acid is successful . Given the difficulties encountered in realizing intermediate 4 using the first approach, the oxidation based strategy was explored next.…”