Epi-Cinchonidine

In 2005, Chen and coworkers found that the epi-cinchonidine/cinchonine-derived thiourea catalysts, 79a,b, can serve as highly active promoters of the Michael addition ofthiophenol to the a,P-unsaturated imide 80 however, the reaction proceeded with low enantioselectivity (up to 17% ee) (Scheme 9.28) [22]. 

The effect of change in the spatial relations at C and C is not clear since, as explained above, there is doubt as to the relative activities of the components of the two pairs, quinine and quinidine, and cinchonidine and cinchonine, but epf-C -quinine and epi-C -quinidine are only slightly active or, according to Dirscherl and Thron, inactive. This result supports Neeman s view that for anti-malarial activity the direction of rotation must be the same at C and C but that does not explain the... 

For each configuration at C.8, two isomers are possible which differ in orientation at C.9. Since all of the alkaloids are identical in configuration except at C.8 and C.9, four isomeric substances are possible in each series. Li one series two of these substances are represented by cinchonine and cinchonidine. The other two members are eptcinchonine and eptcinchonidine. Quinine, quinidine, eptquinine and eptquinidine constitute another such series. The normal members of these series are the major natural alkaloids. The epi compounds may occur naturally... 

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