Pseudoguaianes

Entry 3 in Scheme 6.11 illustrates the application of a c/s-divinylcyclopropane rearrangement in the prepartion of an intermediate for the synthesis of pseudoguaiane-type natural products. 

Reaction of 4 with lithium dimethylcuprate (2 equiv.) in THF effects /3-addition and intramolecular alkylation to 5, but in only 15% yield. Use of methylmagnesium chloride (2 equiv.) and the dimethyl sulfide complex of copper(l) bromide (1 equiv.) increases the yield to 25%. The product is easily dehydrated by TsOH to two isomeric pseudoguaianes (70% yield). 

Lansbury, P.T., Galbo, J. P., and Springer, J.P., An enantioselective approach to chiral pseudoguaian-olide intermediates. Tetrahedron Lett., 29, 147, 1988. 

New additions to the guaiane family include sclerosporin (609), sclerosporal (610), sclerosporene (611), the guaienes (612) and (613) [which co-occurs with precatabrone (614)], and the guaioxide (615). The unusual pseudoguaiane caespitenone (616) has been isolated from the liverwort Porella caespitans This compound co-occurs with (-i-)-aristolone (617) and (-)-a-eudesmol (618), which are enantiomeric to those found in higher plants. 

The same kind of rearrangement has been utilized in an intramolecular sense to transform the much more readily available decalin system into the bicyclo[5.3.0]decanes of the guaiane and pseudoguaiane sesquiterpenes. Thus, the Heathcock group synthesized confertin, as shown in Scheme 46 [82]. 

The Wender group has extensively studied the Q+T)-meta photocycloaddition reaction of double bonds and benzenoids, which furnishes highly condensed polycyclic compounds not accessible by other means. An intramolecular version, with the correct spacer, can produce such a situation as shown in Scheme 60, whereupon uiuaveling leads to the pseudoguaiane rudmollin [98]. 

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