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- Title
The Rickiols: 20‐, 22‐, and 24‐membered Macrolides from the Ascomycete <italic>Hypoxylon rickii</italic>.
- Authors
Surup, Frank; Kuhnert, Eric; Böhm, Andreas; Pendzialek, Tim; Solga, Danny; Wiebach, Vincent; Engler, Hauke; Berkessel, Albrecht; Stadler, Marc; Kalesse, Markus
- Abstract
Abstract: In preceding studies the neotropical ascomycete <italic>Hypoxylon rickii</italic> turned out to be a prolific source of new secondary metabolites, considering that we had obtained terpenoids with five different scaffolds along with a series of terphenyls. From the mycelial extracts of a 70 L scale fermentation of this strain we additionally isolated nine new macrolides (<bold>1</bold>–<bold>9</bold>) by RP‐HPLC. The planar structures were elucidated by NMR spectroscopy complemented by HR‐ESIMS. The relative configurations were assigned by <italic>J</italic>‐based configuration analyses and confirmed by Kishi′s Universal Database. Subsequently, the absolute configurations were assigned by Mosher′s method using the shift analysis of a tetra‐MTPA derivative. For rickiol A (<bold>1</bold>) and E (<bold>5</bold>) we observed transesterification of 20‐membered ring structures to 22‐membered isomers rickiol A2 (<bold>6</bold>) and E2 (<bold>7</bold>), and to 24‐membered isomers rickiol A3 (<bold>8</bold>) and rickiol E3 (<bold>9</bold>), respectively. Cytotoxic effects and moderate antibiotic activity against Gram‐positive bacteria were observed for <bold>1</bold>–<bold>8</bold> and <bold>1</bold>–<bold>6</bold> and <bold>8</bold>, respectively. The total synthesis of rickiol E3 (<bold>9</bold>) established easier access to these compounds.
- Subjects
POLYKETIDES; MACROLIDE antibiotics; ASCOMYCETES; HYPOXYLON; TRANSESTERIFICATION; ISOMERS
- Publication
Chemistry - A European Journal, 2018, Vol 24, Issue 9, p2200
- ISSN
0947-6539
- Publication type
Article
- DOI
10.1002/chem.201704928