Flavomannin derivatives

It can be summarised that the different methods of kinetic resolution and the synthetic correlations have led to the determination of stereochemistry at the biaryl linkage of atrivirin and flavomannin derivatives. Because the position and shape of the CD couplet around 275 nm is not much influenced by substituents present in the two halves of the dimers (refs. 3, 23), several other pigments can now be correlated. It will however need the development of further methods to elucidate the stereochemistry of the phlegmacin group and to determine the configuration of the chiral centers located in the alicyclic rings of the dimers. 

By far the most diverse group of dimeric pre-anthraquinones in regard to number and distribution are the flavomannin derivatives (Table 33). Interestingly, compounds of this type are not restricted to Cor-tinarius, subgenus Phlegmacium, but also occur in Dermocybe and in yellow Tricholoma species. Whereas Cortinarius and Dermocybe are closely related, the systematic relationship to Tricholoma is less obvious. 

The most common flavomannin derivative is the 6,6 -di-0-methyl ether, FDM (348), which occurs in both of its atropisomeric forms in Cortinarius. In Tricholoma auratum (=T. equestre) a mixture of FDM diastereoisomers, racemic at the biaryl linkage, is present. 

To obtain additional proof for the absolute configuration of the flavomannin group, we tried to carry out a synthesis starting with a diphenic acid derivative of known absolute configuration (Scheme 9). 

Gluchoff, K., and W. Steglich Les Pigments de Tricholoma sulphureum Fr. ex Bull. Identification de Nouveaux Derives de la Flavomannine. Trav. mycol. dedies a R. Kiihner, Bull. Soc. Linneenne de Lyon 1974,163. 

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