The Isolation of A New Lactarane Furan From Injured Fruit Bodies of Lentinellus Cochleatus

Abstract

The isolation of a new lactarane furan, called cochleol, formed in injured fruit bodies of Lentinellus cochleatus from stearoylvelutinal, is reported. The structure of cochleol was determined by a combination of spectroscopic and computational methods.Key words. Fungal metabolite, sesquiterpene, lactarane, furan. INTRODUC TION.The fruit bodies as well as the mycelium of the Basidiomycete Lentinellus COC hleatus have been shown to contain the sesquiterpenoid stearoylvelutinal 1 as the principle responsible for the color reaction with the sulfovanillic test mixture, used to identify mushrooms.' Stearoylvelutinal 1 has also been isolated from fruit bodies of apparently unrelated species, belonging to for example the genera Lacta riuL Pussula, Peniophora, Auroscalpium and Artomyces.l.2 In the pungent J.actariuS species, stearoylvelutinal 1 is enzymatically converted to antibiotic and pungent sesquiterpenes as a response to physical injury to the fruit bodies, and has been proposed to be the ammunition in a chemical defense system.3 The possibility that similar conversions also take place in injured fruit bodies of Lentinellus COC hleatus was therefore investigated by comparing extracts of intact and injured specimens, by the technique described earlier.3 RESULTS AND DISCUSSION. TLC analysis of ethyl acetate extracts of intact fruit bodies indicated that stearoylvelutinal 1 is the major extractable constituent, although trace amounts of other compounds also were present. Stearoylvelutinal 1 was 65 Downloaded by [Columbia University] at 03:48 09 December 2014 66 ZIJIE PANG et a/.isolated and the NMR data were found to be identical to those previously reported.4 The compound was also present in extracts made of fruit bodies that had been ground in a meat grinder (to simulate injury) 20 minutes before extraction, although the amounts were smaller. In addition, the presence of a new compound formed in the ground fruit bodies was indicated. This was isolated by column chromatography, and studied by NMR and mass spectroscopy. We proposed the name cochleol for the compound. 3 6 Figure 1.High resolution mass spectroscopy suggested that its elemental composition is C15H20O2, and 1H and 13C NMR data suggested the presence of a 3,4 disubstituted furan, a trisubstituted double bond, an isolated -CH(CH3)-CHz-fragment, two isolated -CH2-groups, and two additional methyl groups (which appears as singlets in the 1H NMR spectrum). The UV absorption spectrum suggested that the double bond is conjugated with the furan ring, and a strong and broad IR band at 3330 cm-l indicated together with a singlet at 84.4 ppm in the 13C NMR spectrum the presence of a tertiary alcohol. The assemblage of these fragments to structure 2 was supported by long-range IH-lH couplings between H-8 and H2-10, and between H-4P and H-5. In order to distinguish between the two possible stereoisomers 2 and 3, extensive Downloaded by [Columbia University] at 03:48 09 December 2014 NEW LACTARANE FURAN 67NOE measurements supporting structure 2 were performed. N0E:s we...

Natural sesquiterpenoids

“…'~' A new lactarane derivative, cochleol (139), has been isolated from injured fruiting bodies of Lentinellus cochleatus. 153 A study of carbon-13 NMR of some protoilludane sesquiterpenes obtained from Armillaria mellea has been carried 156 The total synthesis of ( -)-ptaquilosin, the aglycone of the potent carcinogen ptaquiloside obtained from bracken fern, has been achieved.157…”