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Chemistry and Stereochemistry of Iridoids, XVfi). -EPC-Synthesis of ( -)-HypnophilinThe synthesis of enantiomerically pure ( -)-hypnophilin (27) from (6R,?R)-( -)-?-hydroxy-3-oxabicyclo[4.3.0]non-1-en-9-one (1) is described. 1 was obtained in 93% yield from catalpol, which is readily available from the aqueous sodium carbonate extract of Picrorhiza kurrooa (Scrophulariaceae). The specific rotation, MS, 'H-and I3C-NMR data of synthetic ( -)-hypnophilin were identical with those of the natural product.Ausgewertet "'nach AMX, "nach ABX. Liebigs Ann. Chem. 1991, 893-902 OVCH Verlagsgesellschaft mbH, D-6940 Weinheim, 1991 0170-2041/91/0909-0893 $ 3.50+ .25/0 I 2 3 R = Bz 24R= H 25 26 27 Liebigs Ann. Chem. 1991, 893 -902 Chemie und Stereochemie der Iridoide, XVI

The synthesis of enantiomerically pure triquinane sesquiterpenes is of interest owing to the remarkable biological activity of some of these natural products. The compounds 1–3, which may be prepared from naturally occurring catalpol on a gram scale, are suitable as chiral building blocks. The absolute configuration of (+)‐3, a precursor of (−)‐coriolin, was established by X‐ray structure analysis.

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lung der Substituenten am Sechsring von 7 und 8 ist durch NOE-Messungen gestiitzt. Das diastereomerenreine Hauptprodukt 4 a wurde durch Ozonspaltung mit (9-3-Hydroxy-3-phenylpropionsaure 9 korreliertr6I. Ebenfalls durch Ozonabbau wurden die Produkte 5 a und 10 mit (51-3-Hydroxybutyrolacton 11r7] bzw. (S)-3-Phenylbutyrolacton 12[81 korreliert.