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Synthesis of the C19–C30 Bis-THF Fragment of Iriomoteolide-13a via Stepwise SN2 Cyclization and Intramolecular syn-Oxypalladation

The C19–C30 bis-THF fragment of the proposed structure of
iriomoteolide-13a has been synthesized. The w-mesyloxy-substituted stereotetrad
possessing three continuous hydroxy groups was generated by anti-aldol reaction and asymmetric
dihydroxylation (AD). Upon heating in pyridine the stereotetrad underwent an SN2
cyclization to form the C19–C22
THF ring. It was followed by an intramolecular syn-oxypalladation of the C28 chiral allylic alcohol to give the
C23–C26
THF ring.