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Inter- and intramolecular hetero-Diels-Alder reactions, 32. Iridoids, 26. Synthesis of bridged homoiridoids from secologanin by tandem-Knoevenagel-hetero-Diels-Alder reactions

✍ Scribed by Tietze, Lutz F. ;Bärtels, Christoph

Publisher
John Wiley and Sons
Year
1991
Tongue
English
Weight
634 KB
Volume
1991
Category
Article
ISSN
0947-3440

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✦ Synopsis

Abstract

The tandem‐Knoevenagel‐hetero‐Diels‐Alder reaction of the chiral enantiomerically pure monoterpene glucoside secologanin (1) with 1,3‐dicarbonyl compounds 6a–d and the analogous compounds 11a–b in the presence of ethylenediammonium diacetate as catalyst leads to the bridged cycloadducts 8a–d and 13a–b in 60–70% yield, except for 8d. Compound 8b can be transformed into 9 by treatment with methanol and into 10 by treatment with water. The cycloadditions are highly regio‐ and stereoselective, affording only the bridged but not the annulated compounds as single diastereomers.

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