The size and positioning of substituents on a tetraene, along with the Woodward-Hoffmann rules, control the relative stereochemistry at the four adjacent chiral centers that are generated in the 8pi/6pi electrocyclization cascade. A biomimetic synthesis of (-)-SNF4435 C and (+)-SNF4435 D exploits these steric effects and allows confirmation of the predicted absolute stereochemistry of the natural products.
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Parker et al. (2004) studied this question.
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