Norsesquiterpene Derivatives from the Roots of Ligularia fischeri

Abstract

Four new norsesquiterpene derivatives with various rare skeletons: 1β-hydroxy-6α-isobutyryloxy-9-noreremophil-7(11),8(10)-dien-8(12)-olide (1), 1β-acetoxy-6α-isobutyryloxy-9-noreremophil-7(11),8(10)-dien-8(12)-olide (2), ligularate (3) and 9-oxoplatyphyllide (4), as well as four known sesquiterpenes, platyphyllide (5), 1-hydroxyplatyphyllide (6), 1α-chloro-6β-isobutyryloxy-9-oxo-10β-hydroxyfuranoeremophilane (7), and 1α-chloro-6β-angeloyloxy-9-oxo-10β-hydroxyfuranoeremophilane (8), have been isolated from an extract of the dried roots of Ligularia fischeri (Compositae). The structures of the new compounds were established by spectroscopic methods including extensive 2D NMR techniques (¹H-¹H COSY, HMQC, HMBC and ¹H-¹H NOESY) and HR‐ESI‐MS. In addition, a plausible biosyntheticpathway for compounds 1, 2 and 3 is described.

Key words

Ligularia fischeri - Compositae - norsesquiterpene - eremophilane

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