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From the culture medium of Verticillium inlertexlum three metabolitcs have been isolated, namely the hexaketidcs sorbicillin ( 1 ) and 2'3'-dihydrosorbicillin ( 2 ), and the dimeric hexaketide bisvertinoquinol ( 3 ). 1 has previously been isolated from Penicillium chrysogenum and also synthesised. Hydrogenation of 1 yielded tetrahydrosorbicillin ( 8 ), 2'5'-dihydrosorbicillin ( 9 ) and 2',3'-dihydrosorbicillin ( 2 ). 2 was also obtained by a BF 3 -catalysed condensation of 2,4-dimethyl-resorcinol ( 5 ) with (4R * , 5S * )-4,5-dibromo-hexanoic acid ( 6 ), followed by debromination with zinc and acetic acid. The structure of the dimeric hexaketide 3 (without absolute configuration) was obtained by X-ray structure analysis. It may be considered to be a Diels-Alder adduct of the quinols 11 and 12 , the latter being related to 1 and 2 , respectively, by simple hydroxylation at C(5). The 1 H and 13 C NMR signals of 3 and its mono-methyl ether 10 are interpreted and compared with the corresponding properties of 1 , 2 , vertinolide ( 4 ), 3-methoxy-2-methyl-2-cyclohexenone ( 14 ), and 2-[(E,E)-2,4-hexadienoyl)]-cyclohexanone ( 13 ). The latter was prepared by acylation of the lithium enolate of cyclohexanone with sorbyl chloride. From the spectra of the hexaketides from V . intertextum several patterns have been extracted which are characteristic for some common and some distinguishing substructures in these natural products. |
