Glutinopallane sesquiterpenes

The only two known natural glutinopallane sesquiterpenes 8.2 and 8.3 were isolated from frozen fruiting bodies of L. glutinopallens extracted with CH2CI2 (74). The two esters were separated by preparative HPLC on a RP-18 column with Me0H-H20, 95 5, the fatty acids being identified by GC after methanolysis, as palmitic and stearic acids. In the EIMS spectra of glutinopallal esters, the molecular ions at 

The fascinating lactone isolactarorufin (9.4), at first discovered in an EtOH extract of L. rufus (75, 76, 77) and later also in L. vellereus (5S) and L. necator, is the only known isolactarane sesquiterpene so far isolated from Lactarius species. Other compounds listed in Part 9 are synthetic derivatives that were prepared for structure elucidation of the parent compound or for investigation of their biological properties. 

The absolute configuration of aldehydes 10.2 and 10.10 was established by hydride reduction to diol 10.13 which showed a positive CD curve and thus a positive skewness of the 2(9),7(8)-diene. 

The lactarane sesquiterpenes 10.2, 10.10, 10.13, containing the 2(9),7(8)-cycloheptadiene ring were submitted to conformational analysis by molecular mechanics and HNMR spectroscopy (9). It was observed that the conformational mobility of each compound is practically restricted to the interconversion of the envelope forms of the cyclopentene ring by contrast, essentially only a single conformation of the seven membered ring, with the 3-methyl group pseudo-equatorially oriented, is populated. This is due to the planarity of either the diene in 10.13 or the diene-carbonyl double bonds in 10.2, 10.10. 

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The only two known natural glutinopallane sesquiterpenes (8.2,8.3) have been isolated from Lactarius glutinopallens (42) (Table 8). Their structures are strictly related to velutinal esters (7.14, 7.15) for the presence of the cyclopropane ring and the 7a,8a-epoxyde, and to rubrocinctals 7.7 and 7.8 for the carbomethoxy group at C-3. 

Drimane, farnesane, glutinopallane, protoilludane, isolactarane, and guaiane sesquiterpenes have been isolated so far in a few Lactarius species therefore, they may be considered chemotaxonomic markers. By contrast, large quantities of marasmane, lactarane and secolactarane metabolites occur in almost all Sections, as reported in Table 24. 

Rearranged marasmane skeletons glutinopallane and isolactarane sesquiterpenes... 

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