Metabolites of bird's nest fungi. Part 6. The synthesis of (±)-cybullol and a new synthesis of (±)-geosmin

Abstract

. Can. J. Chem. 54,3276 (1976).The stereoselective transformation of 6,10-dimethyl-4-octal-3-one (8) to racemic cybullol (I), a mztsbolite of C y u r l 7~~~ hlr1ler.i Brodie. is reported. The transformation 4.1O-dimethyl-4-octal-3-one to (i-)-geosmin (15) is described. The results of the photosensitized [4 + 21 cycloaddition of oxygen to a number of IO-metl1yl-2,4-hexalins are discussed. WILLIAM A. AYER, LOIS M. BROWNE et STEVEN FUNG. Can. J. Chem. 54, 3276 (1976).On rapporte la transformation stCrCosClective de la dimethyl-6,10 octal-4 one-3 (8) en cybullol racemique (I), un mitabolite du Cj.utl~us bzrlleri Brodie. On dCcrit la transformation de la dimethyl-4,10 octal-4 one-3 en (i-)-geosn~ine (15). On discute des resultats obtenus lors de la cycloaddition photosensibilisCe [4 + 21 de I'oxygene B un certain nombre de methyl-I0 hexalines-2,4.[Traduit par le journal]Examination of the metabolites of some of the small gastromycetous fungi known as Bird's Nest fungi (Nidulariaceae) in these laboratories has led to the isolation of a variety of terpenoid (e.g., Cyathut helenae Brodie (I), Cyathus bulleri Brodie (2)) and non-terpenoid (e.g., Cyathu~ intermedius (3)) constituents. We now wish to report the stereoselective synthesis of racemic cybullol (I), a degraded eudesmane-type sesquiterpene produced by C. hulleri (2). At the same time we report a new, high yield, synthesis of the related fungal metabolite, geosmin (4).Cybullol, 1, is a dimethyldecalindiol in which the two hydroxyl groups bear a cis-1,4-relationship in a trans-fused system. A facile synthetic approach to a cis-l,4-cyclohexanediol system involves the [4 + 21 cjlcloaddition of a 1,3-cyclohexadiene with molecular oxygen to give a cyclic peroxide, followed by reduction, as outlined in Scheme 1.It is well documented that the photooxygenation of steroidal conjugated dienes is sensitive to steric effects (oxygen as a dienophile, ref. 5a; sensitized photooxygenation of olefins, ref. 56) and that the endo-peroxide produced is usuall) on the side opposite to nearby angular methyl groups. However, relatively few examples of photooxygenation of hexalin dienes have been reported (6). In order to further investigate the stereochemistry of photooxygenation of hexalin systems as well as to provide a model compound for a 13C nuclear magnetic resonance (cmr) study reported elsewhere (7), we examined initially the photooxygenation of 10-methyl-2,4-hexalin, 4 (Scheme 2). The diene 4 was prepared from lO-methyl-4-octal-3-one (8) by the method of Dauben et al. (9). Photosensitized oxygenation (5, 6) in the presence of eosin Y yielded the endo-peroxide 5 and the y-hydroxyenone 6. Catalytic hydrogenation of the etzdo-peroxide gave a crystalline diol, which was assigned the relative stereo- For personal use only.

Off‐flavors in pond‐grown ictalurid catfish: Causes and management options

“…Geosmin production has also been detected in certain species of fungi such as Cyathus bulleri (Ayer, Browne, & Fung, ; Ayer & Paice, ), Chaetomium globosum (Kikuchi, Kadota, Suehara, Nishi, & Tsubaki, ), and Penicillium spp. (Larsen & Frisvad, ; Mattheis & Roberts, ).…”

Carbon‐13 NMR Studies: 82. Carbon‐13 spectra of several 10‐methyl‐cis‐decalins. Conformational preferences of some cis‐decalin derivatives

“…It was of * Author to whom correspondence should be addressed. 13 interest, therefore, to compare these results with those for several of the corresponding cis-decalins. Since the latter are conformationally mobile, the temperature dependence of each of the spectra must be examined to obtain data under conditions of slow exchange for each observable nonequivalent site.…”

The stereochemical dependence of 13C nuclear magnetic resonance chemical shifts and 13C–31P couplings in some dialkylphosphonocyclohexanes

“…It appears therefore that even for second row elements the trans-y shielding effect (9) is not completely general. Recently some examples of marked deslzielding trans-y effects (up to 4 ppm) have been noted (11) in arrangements such as that depicted below, where both the a and the P carbons are quaternary.…”

“…9 (R = Et) 11 (R =;-PI-) 12 ( R = i-Pr) shielded by 4.4 and 3.1 ppm, respectively, in the axial isomer 1. The observation of increased shielding for the carbon bearing the axial substituent has ainple precedent (1-3) but is not always predictable (8).…”