2,5-Dichloro-6-O-Methylnorlichexanthone and 4,5-Dichloro-6-O-Methylnorlichexanthone, Two New Xanthones From an Australian Dimelaena Lichen

Abstract

2,5-Dichloro-6-O-methylnorlichexanthone (8) (2,5-dichloro-1,3-dihydroxy-6-methoxy-8-methyl-9H-xanthen-9-one) and 4,5-dichloro-6-O-methylnorlichexanthone (9)(4,5-dichloro-1,3-dihydroxy-6-methoxy-8-methyl-9H-xanthen-9-one) have been synthesized and shown to co-occur with norstictic acid, connorstictic acid, atranorin, 6-O-methylarthothelin (4), 2,4,5- trichlorolichexanthone (5), 1,3,6-tri-O-methylarthothelin (6) and thiophaninic acid (7) in an Australian Dimelaena lichen.

Xanthones from Fungi, Lichens, and Bacteria: The Natural Products and Their Synthesis

“…Closely related species are isoarthothelin ( 20 , from Buellia sp., ,, Lecanora broccha , , Lecidella asema, L. meiococca , L. vorax, L. subalpicida , Sporopodium phyllocharis (Mont.) Mass., and 3- O -methylarthothelin ( 21 , from D. australiensis and Dimelaena sp …”

“…australiensis , Pertusaria cicatricosa , L. flavo-pallescens , and L. reuteri ), 2,4,7-trichloronorlichexanthone ( 88 , from Lecanora sulphurata, L. flavo-pallescens , and L. reuteri ), 2-chloro-3- O -methylnorlichexanthone ( 89 , isolated and synthesized by Elix and co-workers), 2-chloro-6- O -methylnorlichexanthone ( 90 , from Lecanora salina, Pertusaria cicatricosa , and P. sulpharata ), 4-chloro-6- O -methylnorlichexanthone ( 91 , from Pertusaria sulpharata ), 5-chloro-6- O -methylnorlichexanthone ( 92 , from Lecanora contractula ), 7-chloro-3- O -methylnorlichexanthone ( 93 , reported by Sundholm), 7-chloro-6- O -methylnorlichexanthone ( 94 , from Lecanora populicola , L. salina , and Lecanora sp. ), 2,5-dichloro-3- O -methylnorlichexanthone ( 95 , from L. behringii , L. contractula , L. populicola, and L. salina ), 2,5-dichloro-6- O -methylnorlichexanthone ( 96 , from Dimelaena sp., Dimelaena cf. australiensis , Lecanora contractula , and Pertusaria cicatricosa ), 2,7-dichloro-3- O -methylnorlichexanthone ( 98 , from Lecanora behringii , L. salina , and Lecanora sp.…”

Lead compounds from nature: Synthesis of natural xanthones and chroman aldehydes that inhibit HIV-1

“…Hydroxyxanthones such as 37 are prepared from accessible starting materials using the GSS reaction (Scheme 3). It requires derivatives of salicylic acid such as 34 and an activated phenol such as phloroglucinol (35). These are heated in the presence of 2-Carboxy-4´-methoxydiphenyl ether (53) was obtained in a 50% yield when ochlorobenzoic acid (51) was condensed with p-methoxyphenol (52) in hot pentyl alcohol, potassium carbonate, and catalytic copper bronze (Scheme 9).…”

“…These are classified as miscellaneous. Examples include two chlorinated compounds (31 34 and 3235 ) from Dimelaena lichen(Figure 15). Miscellaneous xanthones from Dimelaena lichen…”