New Dihydrobenzofurans and Triterpenoids from Roots of Microglossa pyrifolia

Abstract

From the roots of Microglossa pyrifolia (Lam.) Kuntze (Asteraceae, tribe Astereae), used in East African traditional Medicine to treat a variety of ailments, seven dihydrobenzofurans and seven triterpenoids (five dammaranes and two 28-nor-oleanenes) were isolated. Their structures were elucidated by spectroscopic (UV, MS and NMR) means. With the exception of the tremetone derivative 1, all of the dihydrobenzofurans found in this drug possess the rare 6-acetyl-5-hydroxy substitution pattern. Dihydrobenzofurans 1 [methyl 2-(5-acetyl-2,3-dihydrobenzo[β]furan-2-yl)propenoate], 3 (methyl2-(6-acetyl-5-hydroxy-2,3-dihydrobenzofuran-2-yl)propenoate] and 7 (6-acetyl-5-hydroxy-2-(1-hydroxy-2-propenyl)-3-methoxy-2,3-dihydrobenzofuran) as well as the triterpenes 3β-acetoxy-25-hydroxydammara-20,23-diene (9), 3β-acetoxy-24-oxo-dammara-20,25-diene (11), 17β-hydroxy-3,16-dioxo-28-norolean-12-ene (12) and 17β-hydroxy-3,11,16-trioxo-28-norolean-12-ene (13) are new natural products, to the best of our knowledge.

Key words

Microglossa pyrifolia - Asteraceae - Astereae - Dihydrobenzofurans - Triterpenes - Structure elucidation

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1 Assignments interchangeable within each row for 10a/10b.