Chromogenic Meroterpenoids from the Mushrooms Russula ochroleuca and R. viscida

Abstract

The spirodioxolactone ochroleucin A1 (1) is responsible for the red colour produced when the stalk base of Russula ochroleuca and R. viscida is treated with aqueous KOH. The labile chromogen rearranges easily into the isomeric dilactoneochroleucin A2 (2). Ochroleucin A1 is accompanied by the biosynthetically related hemiacetal ochroleucin B (5). The new compounds, whose structures were established by MS and NMR methods, appear to be derived biosynthetically by oxidative condensation of two monomeric units. One of them, 2,5‐dihydroxy‐4‐(3‐methylbut‐3‐en‐1‐ynyl)benzaldehyde (6), was detected in the crude toadstool extract by GC/MS comparison with a synthetic sample. The absolute configurations of the ochroleucins A1 and B have been determined by quantum chemical calculation of their CD spectra. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

Oxidative Heck desymmetrisation of 2,2-disubstituted cyclopentene-1,3-diones

“…The 2,2-disubstituted cyclopentene-1,3-dione core is found in several biologically active natural products, including madindolines A and B, 1 similin A 2 and ochroleucin A 1 , 3 and metabolites such as preussidone 4 and involutone 5 (e.g. Figure 1).…”

Studies on the Biosynthesis of Bovilactone‐4,4 and Related Fungal Meroterpenoids

“…[21] Hydrolytic ring-cleavage of the 1,3-dicarbonyl moiety, followed by lactonization of the resulting carboxylic acid 17, would then afford bovilactone-4,4 (3). [21,22] Similar reactions are probably involved in the biosyntheses of gomphilactone, [23] ochroleucin A 2 , [21] the Embelia [10a] and Aegiceras [24] lactones and the parathesilactones, [10c] and in the chemical syntheses of bovilactone-4,4 [8] and related dilactones. [8,10b,17] The rearrangement of dibenzoquinones of type 14 into 4-ylidene butenolides was first described by Posternak.…”

Pigments of higher fungi - a review

“…and R. viscida Kudrna (Russula Pers., Russulaceae). The labile yellow ochroleucin A (78) is rapidly transformed to the stable red ochroleucin B (79) (Sontag et al 2006). Dimeric meroterpenoid pigments have been reported from the Albatrellus Gray species (Albatrellaceae), which included e.g.…”