P-46 海産毒アザスピロ酸-1の全合成研究(ポスター発表の部)

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Azaspiracid-1 (1) is a causative toxin for a new type of shellfish poisoning syndrome named azaspiracid poisoning (AZP), prevailed since November 1995 at a coastal region in Europe. After isolation and structural elucidation by a group led by Yasumoto and Satake at Tohoku University in 1998, the first total synthesis and the structural revision of 1 were made by the Nicolaou group in 2004. We have been working toward total synthesis of 1 to clarify the molecular mechanism of AZP. Here we report our efforts toward this goal and the synthesis of the C_<21>-C_<40> EFGHI-ring fragment 2. Our retrosynthetic analysis of 1 generated the C_<21>-C_<40> fragment 2, which would be assembled with the C_1-C_<20> fragment by the coupling between a benzotriazole amide and a sulfonylpyran. The synthesis of 2 started with a coupling between the C_<36>-C_<40> dithiane 6 and the C_<28>-C_<35> epoxide 7, prepared from the known meso-diol 8 and D-glutamic acid, respectively. Manipulations of the protecting groups and subsequent spiroaminal formation using a catalytic amount of Yb(OTf)_3 delivered the desired spiroaminal 22 stereoselectively. After leading to the corresponding aldehyde 4, the key coupling reaction with the allylic stannane 3 was carried out by using InCl_3 to afford homoallylic alcohol 33 in good yield. Finally, the FG-ring was constructed by the action of HF-pyridine to accomplish the synthesis of the suitably protected C_<21>-C_<40> fragment 2. The total yield was 0.025% for the longest linear pathway from D-glutamic acid (37 steps).
天然有機化合物討論会の論文
2006-09-15

P-46 海産毒アザスピロ酸-1の全合成研究(ポスター発表の部)

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