2003 Pyran derivatives

Pyran derivativesR 0340 Efficient Strategy for Convergent Synthesis of trans-Fused Polycyclic Ethers

Based on an Intramolecular SmI2-Promoted Cyclization of Iodo Ester. —A convergent strategy for the construction of a trans-fused 6-6-6-6-membered tetra-cyclic ether ring system is developed. The key steps involve coupling of two cyclic ethers (II) and (III) by esterification followed by SmI2-promoted intramolecular reduc-tive cyclization. Subsequent hydroboration of dihydropyran (V), intramolecular acetal-ization and Lewis-acid catalyzed silane reduction affords the target compound (X). — (KAWAMURA, K.; HINOU, H.; MATSUO, G.; NAKATA*, T.; Tetrahedron Lett. 44 (2003) 28, 5259-5261; Inst. Phys. Chem. Res., RIKEN, Wako, Saitama 351-01, Japan; Eng.) — M. Paetzel

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