Jd. White et al., Transannular nitrone cycloaddition. A stereocontrolled entry to the spirocyclic core of pinnaic acid, ORG LETT, 3(3), 2001, pp. 413-415
[GRAPHICS]
Thermolysis of lactone 18 initiated a stereospecific transannular nitrone-o
lefin [3 + 2] cycloaddition to yield tetracycle 19, Methanolysis followed b
y reductive cleavage of the isoxazolidine yielded 20, representing the azas
pirocyclic core of pinnaic acid (1).