Gymnopilus spectabilis has been known as a hallucinogenic mushroom from which toxic polyisoprenepolyols such as gymnopilin have been isolated. Since similar mushroom G. aeruginosus has not been known its toxicity, we have investigated its components to isolate two types of polyisoprenepolyols, homologues of gymnopilin and gymnoprenol. The gymnopilin homologue contained an extra isoprene unit compared with known gymnopilin isolated from G. spectabilis. Because of that gymnopilin showed the neuroexitatory activity, G. aeruginosus should be regarded as a poisonous mushroom. For determination of the stereochemistry of newly isolated congeners, we have demonstrated a new procedure for analyzing the configuration at C-3' of hydroxymethylglutaric acid (HMGA) part. The absolute configuration of the ω-tert-hydroxyl was determined as S which implied the configuration of other tert-hydroxyls in 1,5-polyol system in gymnopilin. Namely, we have isolated gymnopilin (3:m=2, n=4) from G. spectabilis and transformed it to γ-Lactone (5). Model lactones having similar asymmetric center at C-5 were synthesized and Cotton effects in CD spectra were compared. γ-Lactone (5) derived from gymnopilin showed positive Cotton effect as shown with S-lactone (25). The above fact proved the S-configuration at ω-position of gymnopilin (3).
