Stille Reactions

The Stille reaction is extremely useful to form diene and stilbene moieties, but suffers from the drawback of requiring poisonous tin compounds. Once again, the polymeric support provides the opportunity to eliminate the tin moieties simply by filtration. Nicolaou demonstrated the synthesis of the 14-membered macrocycle (S)-Zearalenon 93 which started from solid phase-bound tin chloride 90. Coupling to a vinyl lithium compound generated 91, and two more steps produced the precursors for cyclization 92. Cyclative Stille coupling finally gave Zearalenon 93. Remarkably, only the E-isomers came off the solid phase by cyclization, whereas the Z-isomers did not cyclize and remained bound to the solid phase (Scheme 25) [36], ha c4h9 . ores h9c4 c4h9 O Snci ~ JSn ()40TBS

90 91

memp o

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