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Three new acylphloroglucinols – myrtucommulone D (1), myrtucommulone E (2), and myrtucommulone C (3) – and a new usnic acid derivative usnone A (4) have been isolated from Myrtus communis L., along with the known acylphloroglucinol myrtucommulone B (5), one sterol 8 and six triterpenes 10–15, two flavonoids 6 and 9, and 2,5‐dihydroxy‐4‐methoxybenzophenone (cearoin; 7). The structures of compounds 1, 2, 4, and 5 were also unambiguously determined by single‐crystal X‐ray diffraction analysis. The compounds 1–3 and 5 were found to be more potent α‐glucosidase inhibitors than the clinically used standard acarbose. Compound 3 exhibited the highest activity among all the acylphloroglucinols, with an IC50 (inhibition concentration) = 35.4 ± 1.15 μM. Compounds 1, 2, 4, 7, and 11–15 also exhibited antibacterial activities.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

Among sesquiterpenes, the most common in Nature and the most intensively studied from all-sided stereochemical aspects are the monocyclic germacranes, of which the bicyclic sesquiterpenes eudesmanes, guaianes, carotanes, and others are considered, to be biogenetic derivatives [1, 2].The germacrane skeleton of these natural compounds is based on the carbon skeleton of cyclodecane with two endocyclic double bonds in the 1(10) and 4(5) positions and methyl groups at C4 and C10 and an isopropyl group at C7, in accordance with the isoprene rule. However, examples are found in which one of the double bonds in the germacranolides is shifted into the 9 = 10 position [3], has been replaced by an epoxide group [4], or is absent [5]. Depending on the cis-or transconfigurations of the endocyclic double bonds (or their substituting epoxide groups) in the 1(10) and 4(5) positions of the cyclodecadiene system, they are classified as representatives of four possible geometric isomers [1, 6]:

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