Synthesis of toxyloxanthone B

Abstract

a b s t r a c tA synthesis of the naturally occurring xanthone toxyloxanthone B is described, in which the key step is the regioselective addition of a methyl salicylate to a substituted benzyne, followed by cyclization of the intermediate aryl anion to form the xanthone, the regiochemistry of the aryne addition being confirmed by X-ray crystallography. Subsequent introduction of the pyran ring by [3,3]-rearrangement and deprotection completed the synthesis.

o-Silylaryl Triflates: A Journey of Kobayashi Aryne Precursors

“…In 2014, Moody and co-workers accomplished a total synthesis of toxyloxanthone B ( 14-76 ) . As shown in Scheme , this synthesis involves an aryne nucleophilic annulation reaction between methyl salicylate 14-72 and o -silylaryl triflate 14-73 , furnishing the xanthone framework 14-74 in regioselective manner.…”

“…In 2014, Moody and co-workers accomplished a total synthesis of toxyloxanthone B (14-76). 931 As shown in Scheme 315, this synthesis involves an aryne nucleophilic annulation reaction between methyl salicylate 14-72 and o-silylaryl triflate 14-73, furnishing the xanthone framework 14-74 in regioselective manner. Consequently, compound 14-75 could be prepared, which was then subjected to Claisen rearrangement conditions with a subsequent universal removal of benzyl protecting groups, giving rise to toxyloxanthone B (14-76) in 64% yield.…”

Recent advances in the synthesis of xanthones and azaxanthones

“…A myriad of examples have been described in the literature, including the reaction with alkyl halides for the transformation into alkoxy, 43,59,69,[219][220][221][222][223] haloalkoxy, 18,51,69,99,224 methyl alkyl-or aryl-piperazine moieties, 225 epoxypropanoxy 65,103,[220][221][222] oxirane 221 , oxypropanolamines, 103 benzenesulfonamides, 226 and propargyloxy. 45,52,54,63,106,118,173,227,228 When reacted with other compounds that are not alkyl halides, several other functional-Scheme 25 Other methodologies for the synthesis of xanthones.…”

Xanthones and Cancer: from Natural Sources to Mechanisms of Action

“…From salicylic acid and phenol in phosphorus pentoxide-methanesulfonic acid [144,170] Benzoxanthone FeCl 3 -Catalyzed, three-components, one-pot [171] Caged xanthones Regioselective Claisen/DielsÀ Alder cascade reaction [151,[172][173][174]175] Haloxanthones From 2-bromofluorobenzenes and salicylaldehydes via palladium-catalyzed acylation-SNAr [167,176,177] Hydroxyxanthone Classical one-step synthesis starting from two aryls induced by Mannich reaction and Eaton's reagents. [167,[178][179][180][181][182] Pyranoxanthones From 1,3-dihydroxyxanthone with different reagents [180] Pyridyl xanthones Ag 2 CO 3 mediated oxidative cyclization [183] Sulfonamides xanthones Eaton's reagent and chlorosulfonic acid [184] Thioxanthones Heteropoly acid, catalytic, under microwave [176,185,186] Toxyloxanthones Regioselective aryne addition and Claisen rearrangement [187] Triazole xanthone…”