Novel Antihyperglycemic Terpenoid-Quinones from Pycnanthus angolensis

Abstract

Two new compounds, pycnanthuquinone A (1) and pycnanthuquinone B (2), were isolated from leaves and stems of the African plant, Pycnanthus angolensis (Welw.) Warb (Myristicaceae), by bioassay-guided fractionation of an ethanolic extract using a diabetic mouse model. Pycnanthuquinones A and B are the first representatives of a novel terpenoid-type quinone skeleton, and both compounds possess significant antihyperglycemic activity.

Nature of the Intermediates in Gold(I)‐Catalyzed Cyclizations of 1,5‐Enynes

“…In general, good yields were obtained with electrophilic catalysts B or C. Enyne 9 n, substituted at the meta position of the aryl ring, led to a mixture of regioisomeric compounds 16 e and 16 e' ( [21] 1,5-Enyne 9 o reacted smoothly with catalyst B at room temperature to give cycloadduct 16 f in 95 % yield, the structure of which was confirmed by X-ray diffraction (Scheme 4). [22] Tricyclic compound 16 f possesses the tricyclic skeleton of (+)-pycnanthuquinone C (17), [23,24] which is a natural compound structurally related to pycnanthuquinones A and B [25] and rossinone. [26] Intermediates of cyclizations of 1,6-enynes have been trapped by intra- [27] or intermolecular cyclopropanation; [18,28] however, the trapping of intermediates 2 by alkenes in cyclizations of 1,5-enynes was unknown.…”

Meroterpenes from Marine Invertebrates: Structures, Occurrence, and Ecological Implications

“…[15] and successively recovered in the viscera extract of A. fugiense , also collected in Antarctica, along with the related compounds 36 – 38 [29] (Figure 4). Rossinone B has a rather novel structural architecture featured by a linearly fused 6-6-5-ring core, which so far has been found in only three plant-derived natural products, pycnanthuquinones A–C [19,30]. The tricyclic framework of 35 supposedly derive from the corresponding linear hydroquinone derivative rossinone A ( 8 ) which has been reported to co-occurr in Aplidium sp.…”

Biomimetische Synthese von (−)‐Pycnanthuchinon C über eine Vinylchinon‐Diels‐Alder‐Reaktion

“…[5,6] Mit Zugang zu reichlich Material waren wir jedoch in der Lage, nOe-Signale zwischen den Protonen beider Hydroxygruppen und des Methinwasserstoffatoms an C6 in wasserfreiem [D 6 ]DMSO zu beobachten. Dies ist nur möglich, wenn das nichtnatürliche (À)-Pycnanthuchinon C die in Abbildung 3 gezeigte relative Konfiguration aufweist.…”

“…[4] Angesichts der Häufigkeit von Chinonen in der Natur ist es durchaus möglich, dass VCDA-Reaktionen in der Biosynthese eine Rolle spielen. In der Tat können viele interessante Naturstoffe mit entsprechenden Retrons identifiziert werden, zum Beispiel die Pycnanthuchinone (1-3), [5,6] Glaziovianol (4), [7] Pleurotin [8] und, in modifizierter Form, Rossinon B (6). [9] Eine retrosynthetische Analyse dieser Naturstoffe führt in den meisten Fällen zu einfachen Meroterpen-Chinonen, die selbst weit verbreitete Naturstoffe sind.…”

“…Zusätzlich konnte die Konfiguration des Isomers 13 aus der röntgenkristallographischen Analyse ermittelt werden, und die trans-Konfiguration des Hydrindan-Gerüsts war aus der Literatur bekannt. [5,6] Aufgrund dieser Daten waren zwei Isomere möglich: 16 und (À)-3 (Abbildung 3).…”