Bicyclo- -nonane derivative structures

The potential of Fischer carbene complexes in the construction of complex structures from simple starting materials is nicely reflected in the next example. Thus, the reaction of alkenylcarbene complexes of chromium and tungsten with cyclopentanone and cyclohexanone enamines allows the di-astereo- and enantioselective synthesis of functionalised bicyclo[3.2.1]octane and bicyclo[3.3.1]nonane derivatives [12] (Scheme 44). The mechanism of this transformation is initiated by a 1,4-addition of the C -enamine to the alkenylcarbene complex. Further 1,2-addition of the of the newly formed enamine to the carbene carbon leads to a metalate intermediate which can... 

Initially the main PBDs isolated from floral resins of Clusia spp. showed to be bicyclo-[3.3.1]-nonane derivatives but a new study demonstrated the presence of several SBDs in these sources. Structures of weddellianone A (24) and B (25), lanceolatone (26) and hilarianone (27) were established on spectroscopic evidences of their methyl derivatives obtained after treatment of fresh floral resins with diazomethane [20], All the structures were represented with a 1,3,5-triketone system because of the treatment before mentioned don t facilitate the determination of the exact structures. On the other hand, many natural SBDs have shown to have methoxyl groups in their structures and then in the methyl derivatives above mentioned is not possible to establish the origin of the methoxyl groups certainly. 

Hyperflorin, an antibiotic isolated from St. John s wort Hypericum perforatum L.), has been found on the basis of chemical and spectroscopic evidence to possess structure (639). ° A review on the conformational analysis of bicyclo[3,3,l]nonanes has appeared,and the conformations of l,5-disubstituted-3,7-dimethyIenebicyclo-[3,3,l]nonane derivatives have been shown, on the basis of lanthanide-induced n.m.r. shifts, to be predominantly in the double-chair form. In a notable paper that contains a wealth of information pertinent to adamantane synthesis, it has been reported that bicyclo[3,3,l]nonane-3,7-dicarboxylic acid, its dimethyl ester, and various derivatives exist mainly in the chair-boat conformation. The synthetic entry to these systems is illustrated for the above diester (643) in which the starting point is adamantanone (640) thus, ring expansion with diazomethane followed by SeOj oxidation gave the a-diketone (641) which was cleaved with periodate to give the diacid (642). Esterification using diazomethane gave (643) which exists, as does the diacid, as... 

Suggest an alternative bicyclo[3.3.1]nonane derivative that might be used to connect the carbons marked by asterisks in structure 6. Suggest tactics that will transform your proposed intermediate into twistane. (Unnatural Products-7)... 

We proposed to group PBDs that present a bicyclo-[3.3.1]-nonane-2,4,9-trione system in accord with benzoyl moiety position type A if it is on C-l, type B if it is on C-3 and finally type C if it is on C-5, Fig.(5) [40]. The structures previously reported as type C, nemorosone and 7-epinemorosone, have been corrected and all polyisoprenylated benzophenones derivatives with a bicyclo-[3.3.1]-nonane-2,4,9-trione system isolated, therefore, are derivatives of type A or B [18,19]. 

The diol derivatives of bicyclo[3.3.1]nonanes (Figure 9) are such systems, and the unique molecular shape of this building block has been used to form self-assembled supramolecular structures and inclusion complexes with various guest molecules. Some derivatives of this ring skeleton, the so-called tubuland diols, give controllable crystal structures with a variety of inclusion guests. 

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