| Project/Area Number |
63470024
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
天然物有機化学
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| Research Institution | Tokushima Bunri University |
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Principal Investigator |
NISHIZAWA Mugio Tohushima Bunri University, Fasalty of Pharmaceutical Sciences, Professor, 薬学部, 教授 (40137188)
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| Co-Investigator(Kenkyū-buntansha) |
YAMADA Hidetoshi Tokushima Bunri University, Faculty of Pharmaceutical Sciences, Instructor, 薬学部, 助手 (90200732)
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| Project Period (FY) |
1988 – 1990
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| Project Status |
Completed (Fiscal Year 1990)
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| Budget Amount *help |
¥7,800,000 (Direct Cost: ¥7,800,000)
Fiscal Year 1990: ¥1,500,000 (Direct Cost: ¥1,500,000)
Fiscal Year 1989: ¥1,500,000 (Direct Cost: ¥1,500,000)
Fiscal Year 1988: ¥4,800,000 (Direct Cost: ¥4,800,000)
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| Keywords | Sweet taste / Diterrene glycosides / Baiyunoside / (<minus-plus>) -Baiyun / Labdanoid / Thermal glycosylation / Koenigs knorr glycosylation / 立体化学制御 / 甘味 / バイユノサイド / バイコノール / グルコシル化反応 / 熱グルコシル化反応 |
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| Research Abstract |
Development of new sweet tasting compounds is important task for organic chemist base on the requirement of diet food. Although a large numbers of sweet tasting terpenoid glycoside have been discovering from a variety of plant source, few synthetic effort have carried out before due to their structural complexity. We interested in the synthetic approach to one of sweet tasting glycoside, baiyunoside, which have labdane type diterpenoid with glucose and xylose functionality. This glycoside was isolated from Chinese drug, Bai-Yun-Shen (***) by Tanaka and co-workers, and reported that 250 times sweeter than sucrose. We expected to synthesize not only natural product but also a variety of synthetic analog in order to enjoy their taste. The synthesis of the aglycone, (<plus-minus>) -baiyunol, have accomplished by mercury (ll) triflate induced biomimetic olefin cyclization of 13-oxo-ambliofuran giving rise to furan containig labdanoid diterpene in highly selective manner. Thus 15 g of racemi
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c aglycone in hand, we focused glycosylation chemistry. For the introduction of glucose and xylose successively, first 2-hydroxyl group discriminated glycosylation have achieved under Koenigs-Knorr condition using silver triflate and tetramethylurea. Introduction of xylose into 2^'-hydroxyl group of monoglycoside have achieved by using Noyori^'s method based on a strong affinity between silicone and fluorine atoms. Deprotection of benzyl groups by Li/NH_3 reduction followed by acetyl groups by methanolysis afforded baiyunoside. The synthetic baiyunoside was identified with natural product with every respects including its sweet taste. Analogously, 24 kinds of related glycosides were prepared and characterized by spectroscopy. Among these glycosides, though (+) -baiyunol with beta-glu-beta-glu showed strong bitter taste, (+) -baiyunol with beta-glu-alpha-glu showed very strong sweet taste. (+) -Baiyunol with beta-glu-alpha-rha was also very sweet. (-) -Baiyunol derivatives did not show any characteristic taste. *^<7,8> Analogs of aglycone were also derived into disaccharides and which showed another strong sweet taste. Thus we prepared 25 kind of diterpenoids, and found that a minor structural change resulted big change of taste. One is very sweet and another is very bitter. During the synthesis, we need to develop much efficient procedure of glycosylation without using any heavy metal salts. We found that neat thermolysis of glycosyl halides with alcohol in the presence of acid scavenger gave glycosides in sufficient yield. Particularly the case of rhamnosyl or mannosyl chlorides afforded alpha-glycosides in high stereoselectivity. According to the newly developed ther mal glycosylation procedure we are currently working for the synthesis of the first cyclooligosaccharide of L-series in order to develop a new area of inclusion chemistry. Less
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