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Paper | Regular issue | Vol 63, No. 3, 2004, pp.539-565
Published online, 9th January, 2004
DOI: 10.3987/COM-03-9952
Synthetic Studies on Azaspiracid, a Novel Shellfish Poison: Attempts to Construct the ABCD Ring System

Yuichi Ishikawa and Shigeru Nishiyama*

*Department of Chemistry, Faculty of Science and Technology, Keio University, Hiyoshi 3-14-1, Kohoku-ku, Yokohama 223-8522, Japan

Abstract

Synthesis of the ABCD ring system of azaspiracid (1) was attempted. Construction of the highly substituted tetrahydrofuran (9) via the Pd(0)-mediated cyclization, followed by spirocyclization afforded trispiro-ring (28), carrying an unnatural ring-junctions. The BCD ring system of 1 was successfully produced by using the bridge of a sulfur atom between the B and C ring to control the spiroacetal center of the C13 position. The stereostructures were unambiguously determined by the NOE experiments.