Norcamphor synthesis

Similarly to 8-lactone 260, y-lactone 263, prepared also from ( )-norcamphor (228), proved to be another useful intermediate for the synthesis of all four corynantheidol stereoisomers as well as of the corresponding 18,19-didehydro derivatives. Cleavage of the a-diketone monothioketal moiety in 263 and the formation of amide 265 by its reaction with tryptamine, followed by Bischler-Napieralski cyclization and sodium borohydride reduction, resulted in a mixture... 

The procedure described herein demonstrates a general synthetic method to form a-methylene ketones by direct methylene transfer. A number of methods have been previously described and reviewed.2 3 The advantages of direct methylene transfer for the formation of a-methylene ketones are the aprotic, nearly neutral conditions utilized. Although the reaction is not regiospecific, it is highly sensitive to steric hindrance, and transfer occurs at the less hindered site of unsymmetrical ketones. The reaction has been applied to cyclic and acyclic ketones4 and extended to the synthesis of vinyl ketones3 and a-methylenealdehydes. It is not applicable to y- or 8-lactones, or strained cyclic ketones such as norcamphor or cyclobutanone. With cyclohexanone, cyclopentanone, or aldehydes as substrates, pre-formation of the iminium intermediate... 

Kawamiua, M.. and Ogasawara, K., Stereo- and enantio-controlled synthesis of (-i-)-juvabione and (-l-)-epijuvabione from (-i-)-norcamphor, J. Chem. Soc.. Chem. Commun., 2403, 1995. 

Takano et a]L. have extended their syntheses of corynantheine relatives from ( )-norcamphor, and have completed the synthesis of the 18,19-dihydro-alkaloids with all four stereochemical conflg-... 

Other synthetic work in this area includes a new synthesis of ( )-iV-benzoyl-meroquinene aldehyde (302), in eighteen steps, from ( )-norcamphor. The lack of stereospecificity in an intermediate reduction stage afforded also a synthesis of the diastereoisomer of (302). 

Bicyclo[2.2.1]heptanes are widely distributed in namre among the bicyclic ter-penes, and the Diels-Alder reaction provides a convenient method for their synthesis. Thus, cyclopentadiene and vinyl acetate react smoothly on warming to form the adduct 49, which is easily transformed into norcamphor 50 and related compounds (3.44). 

The intermediate ( )-meroquinene aldehyde, in the synthesis of the cinchona alkaloids, continues to excite interest and a new synthesis from ( )-norcamphor... 

Kawamura, M. Ogasawara, K. "Stereo- and Enantio-controlled Synthesis of (+)-Juvabione and (+)-Epljuvabione from (+)-Norcamphor J. Chem. oc.. Chem. Commun. 1995, 2403-2404. 

The last VCD example by Lattanzi et al. describes the use of VCD and DFT calculations to assign the absolute configuration of a recently prepared (15,4/ )-norcamphor-derived furyl hydroperoxide, (+)-8, introduced as a less hindered and more reactive stereoselective oxidant in organic synthesis. During the preparation of 8 through the hydroperoxidation of an alcohol precursor via nucleophilic substitution, it is expected that epimerization will occur at carbon 2 of the bicyclic framework leading to the formation of either exo- or endo-8 (Figure 53.25). Therefore, the... 

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