- Regioselective single pot C3-glycosylation of strophanthidol using methylboronic acid as a transient protecting group
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This manuscript describes a single pot protocol for the selective introduction of unprotected sugars to the C3 position of the cardiotonic steroid strophanthidol. These reactions proceed with high levels of regiocontrol (>20:1 rr) in the presence of three other hydroxyl functionalities including the C19 primary hydroxyl group and could be applied to different sugars to provide the deprotected cardiac glycosides upon work up (5 examples, 77–69% yield per single operation). The selective glycosylation of the less reactive C3 position is accomplished by the use of traceless protection with methylboronic acid that blocks the C5 and C19 hydroxyls by forming a cyclic boronic ester, followed by in situ glycosylation and a work up with ammonia in methanol to remove the boronic ester and the carbohydrate ester protecting groups.
- Tay, Jia-Hui,Dorokhov, Valentin,Wang, Sibin,Nagorny, Pavel
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p. 437 - 448
(2019/04/10)
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- Corchorusosides A, B, C, D, and E, new cardiotonic oligoglycosides from the seeds of Corchorus olitorius L. (Moroheiya)
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The methanolic extract of the seeds of Corchorus olitorius L. (Moroheiya) was found to show inhibitory effect against Na+,K+-ATPase and positive inotropic activity in the guinea pig isolated atria. Through bioassay-guided separation from the methanolic extract, new cardenolide oligoglycosides called corchorusosides A, B, C, D, and E were isolated together with six known cardenolide oligoglycosides. The structures of new corchorusosides were determined on the basis of chemical and physicochemical evidence. All cardenolide oligoglycosides from the seeds showed potent inhibitory activity against Na+,K+-ATPase, which was equivalent to those of digitoxin and ouabain. The methanolic extract, glycoside fraction, and principal glycoside showed potent acute toxicity by intraperitoneal administration, whereas they showed little acute toxicity by oral administration. Furthermore, by means of HPLC quantitative analysis of the cardiotonic oligoglycosides, it was found that the glycosides mainly distributed in the seeds , while the edible parts such as fresh young leaves and stems contained only trace amount.
- Yoshikawa, Masayuki,Murakami, Toshiyuki,Shimada, Hiromi,Fukada, Nobuyuki,Matsuda, Hisashi,Sashida, Yutaka,Yamahara, Johji
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p. 869 - 873
(2007/10/03)
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