Furyl‐ und Thienyl‐benzochinone, eine Gruppe neuer Farbstoffe

Meroterpenoid Pigments from Albatrellus flettii (Basidiomycetes)

“…This indicates that the colour originates from electronic interactions between the benzoquinone and the conjugated furan chromophore [12] and not from a charge transfer interaction of the quinone with the remote resorcinol group. 2-Hydroxy-3,6-dimethyl-1,4-benzoquinone (10) [10,17] was prepared from 2,5-dimethylbenzoquinone via 1,2,4-triacetoxy-3,6-dimethylbenzene and 3,6-dimethylbenzene-1,2,4-triol according to literature procedures.…”

“…This reflects the importance of the additional alkyl chain at the furan ring for the coupling reaction. [12] Experiments to enhance the reaction rate by adding Lewis acid catalysts such as BF 3 , ZnCl 2 , AlCl 3 or traces of HCl or AcOH were unsuccessful [13] and caused the formation of uncharacterized green "polymers" due to the instability of cristatic acid (3) under acidic conditions. [2] The addition of oxidizing agents such as DDQ, [14] useful for the quinone-furan coupling in simple cases, is known to convert ortho-polyprenylated phenols into the corresponding chromenes.…”

Pigments of fungi (macromycetes)

“…On the basis of this observation, Steglich suggested that the colour originated from electronic interactions between the benzoquinone and the conjugated furan chromophore rather than from a charge transfer interaction of the quinone with the remote resorcinol group. 87 Tridentoquinone 181, the main pigment of Suillus tridentinus, was accompanied by its dimer tridentorubin 182 and deoxytridentoquinone 183. The absolute configuration of 181 was established as 14 0 R by a single-crystal X-ray diffraction analysis of the corresponding (À)-camphanoate.…”