Natural products are an indispensable source for drug discovery. The major challenge for exploiting this evolutionary optimized pool of potential lead structures is the fast and reliable recognition of known compounds, i. e. dereplication. This task is essential for the discovery
process in high-throughput screening scenarios, since it allows the focus to be placed on novel chemical structures at an early stage. Furthermore, information on identified compounds will help to rationalize observed bioactivities. This article describes an effective, library-supported strategy
for the dereplication of crude extracts and pre-fractionated samples, using an HPLC-based multidetector platform and NMR techniques, respectively.
In the preceding paper1) the isolation and biological properties of eight lactones from the ascomycete A111-95 is described (compounds 3 and 4 were obtained as a mixture), while this part discusses the determination of their chemical structures. Seven of the compounds, 1-7, are 5-membered lactones of what appears to be the same biosynthetic pathway, while 4-methoxy-6-pentylpyrone (8) appears not to be related with the others. The strongest nematicidal effect was demonstrated by the mixture of 3 and 4, while galiellalactone (7) was shown to be a moderately cytotoxic agent.Compounds 1, 3 and 4 are new compounds while compound 22) and galiellalactone (7)3) previously have been reported from cultures of Galiella rufa, although the structure elucidation of 2 was never discussed (the structure of galiellalactone (7) was determined by X-ray crystallography). Pregaliellalactone (5)4), desoxygaliellalactone (6)5) and the pyrone 86) have been
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