138(P-92) パラジウム(II)触媒を用いる環化反応の開発、及びアザ糖を含む天然物の全合成(ポスター発表の部)

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Stereoselective amino cyclization of alkenyl amines is one of the most important methodologies for the stereoselective construction of nitrogen hetero alicycles. We have developed an intramolecular substitution of an allylic alcohol by a heteroatom using palladium(II) catalyst without activation of an allylic alcohol. Recently many aza-sugars were found to be efficient inhibitors of the carbohydrate hydrogenase and transferase. Herein we report the total synthesis of 1-deoxymannojirimycin as aza-sugar and the related natural compounds by using Pd(II) catalyzed cyclization. 1) Total synthesis of (-)-hydroxysedamine (-)-Hydroxysedamine is a piperidine alkaloid, isolated from Sedum acre. The urethane 9 was prepared from (S)-glycidol. Treatment of PdCl_2(CH_3CN)_2 gave the cyclized mixture in 48% yield, the ratio of which was 8:1. The major isomer was converted to (-)-Hydroxysedamine's synthetic intermediate in 8 steps. 2) Total synthesis of SS20846A SS20846A is a piperidine alkaloid, isolated from Streptomyces sp. S20846. The urethane 28 was prepared from (S)-glycidol. Treatment of PdCl_2(CH_3CN)_2 afforded the cyclized mixture in 89% yield, the ratio of which was 85:15. The major isomer was converted to SS20846A in 9 steps. 3) Total synthesis of 1-deoxymannojirimycin The urethane 38 was prepared from 3,4-di-O-benzyl-5,6-O-isopropylidene-D-mannitol. Treatment of PdCl_2(CH_3CN)_2 gave the cyclized mixture in 86% yield, the ratio of which was >26:1. Conversion of this product to 1-deoxymannojirimycin was effected by the 3 steps sequence shown in Scheme 13. In conclusion, we have described a novel asymmetric synthesis of the α-glycosidase inhibitor 1-deoxymannnojirimycin started from D-mannitol. The key step in the sequence is the palladium-catalyzed cyclization of the urethane.
天然有機化合物討論会の論文
2000-10-01

138(P-92) パラジウム(II)触媒を用いる環化反応の開発、及びアザ糖を含む天然物の全合成(ポスター発表の部)

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