12. QUINONES: STRUCTURE AND DISTRIBUTION
655
and phoenicin (LXXXV) have a structural relationship like that of
spinulosin and fumigatin, but have not been found in the same genus.
Penicillium rubrum O. Stoll (104) elaborates both phoenicin and its
leuco compound, and the strain of Aspergillus fumigatus which synthesizes fumigatin, also produces the corresponding quinol, the quinone:
quinol ratio varying according to the stage of development of the
organism. An unusual metabolite is formed by a Gliocladium species
(probably G. roseum Bainier) (105) when grown on Raulin-Thom
solution; in addition to an orange quinone, aurantiogliocladin (LXXX),
and its dark red quinhydrone, rubrogliocladin, it yields a colorless reduction product gliorosein (LXXXI), isomeric with aurantiogliocladin
quinol. This is the only naturally occurring quinol in the benzene series
that is known in the tautomeric diketo form. [There is also one example
in the naphthoquinol series (XLVII).] Another unusual derivative of
2,3-dihydrobenzoquinone is the optically active epoxide terreic acid
(LXXIX), a metabolic product of Aspergillus terreus (106).
The terphenylquinones (LXXXVII) to (XCII) are a unique group
of natural products, confined to the Agaricales (excepting volucrisporin,
as already mentioned) and certain lichens. They are all derivatives of
2,5-diphenylbenzoquinone with a varying pattern of hydroxylation reminiscent of flavonoids and are mostly dark brown in color. The bronze
pigment polyporic acid (LXXXVII) constitutes 23% of the dry weight
of Polyporus rutilans (Pers.) Fries (107). Thelephoric acid, which is
accompanied by anthraquinone pigments in Polystictus versicolor (108)
was thought formerly to be a phenanthrenequinone (109), but work in
several laboratories has shown that it belongs to the terphenylquinone
group and Gripenberg (110) has very recently established the pentacyclic structure (XCII) by synthesis. Volucrisporin (LXXXIX), the only
quinone of this group found in a lower fungus, differs from the others
in the absence of oxygen functions on the quinone ring and in the rare
existence of m-hydroxyphenyl groups (111). Both the red pigment
and its quinol are present in the metabolism solution of Volucrispora
aurantiaca Haskins. Unusual reduction products are also a feature of
these quinones. Leucomelone (XC), the brown pigment present in
the black edible mushroom Polyporus leucomelas Pers. ex Fr., is accompanied by a colorless compound, protoleucomelone, which is the
hepta-acetate of leucomelone quinol (112). Aurantiacin, the dark red
3,6-dibenzoate of atromentin (LXXXVIII) is found in
Hydnum
aurantiacum Batsch, together with its leucodibenzoate and theleporic
acid (113). Atromentin itself occurs mainly in a reduced form in
Paxillus atrotomentosus (Batsch) Fr., for only the exterior of the
fungus is colored. As the quinone was isolated by alkaline extrac-
655
and phoenicin (LXXXV) have a structural relationship like that of
spinulosin and fumigatin, but have not been found in the same genus.
Penicillium rubrum O. Stoll (104) elaborates both phoenicin and its
leuco compound, and the strain of Aspergillus fumigatus which synthesizes fumigatin, also produces the corresponding quinol, the quinone:
quinol ratio varying according to the stage of development of the
organism. An unusual metabolite is formed by a Gliocladium species
(probably G. roseum Bainier) (105) when grown on Raulin-Thom
solution; in addition to an orange quinone, aurantiogliocladin (LXXX),
and its dark red quinhydrone, rubrogliocladin, it yields a colorless reduction product gliorosein (LXXXI), isomeric with aurantiogliocladin
quinol. This is the only naturally occurring quinol in the benzene series
that is known in the tautomeric diketo form. [There is also one example
in the naphthoquinol series (XLVII).] Another unusual derivative of
2,3-dihydrobenzoquinone is the optically active epoxide terreic acid
(LXXIX), a metabolic product of Aspergillus terreus (106).
The terphenylquinones (LXXXVII) to (XCII) are a unique group
of natural products, confined to the Agaricales (excepting volucrisporin,
as already mentioned) and certain lichens. They are all derivatives of
2,5-diphenylbenzoquinone with a varying pattern of hydroxylation reminiscent of flavonoids and are mostly dark brown in color. The bronze
pigment polyporic acid (LXXXVII) constitutes 23% of the dry weight
of Polyporus rutilans (Pers.) Fries (107). Thelephoric acid, which is
accompanied by anthraquinone pigments in Polystictus versicolor (108)
was thought formerly to be a phenanthrenequinone (109), but work in
several laboratories has shown that it belongs to the terphenylquinone
group and Gripenberg (110) has very recently established the pentacyclic structure (XCII) by synthesis. Volucrisporin (LXXXIX), the only
quinone of this group found in a lower fungus, differs from the others
in the absence of oxygen functions on the quinone ring and in the rare
existence of m-hydroxyphenyl groups (111). Both the red pigment
and its quinol are present in the metabolism solution of Volucrispora
aurantiaca Haskins. Unusual reduction products are also a feature of
these quinones. Leucomelone (XC), the brown pigment present in
the black edible mushroom Polyporus leucomelas Pers. ex Fr., is accompanied by a colorless compound, protoleucomelone, which is the
hepta-acetate of leucomelone quinol (112). Aurantiacin, the dark red
3,6-dibenzoate of atromentin (LXXXVIII) is found in
Hydnum
aurantiacum Batsch, together with its leucodibenzoate and theleporic
acid (113). Atromentin itself occurs mainly in a reduced form in
Paxillus atrotomentosus (Batsch) Fr., for only the exterior of the
fungus is colored. As the quinone was isolated by alkaline extrac-