Clonorosins A (1) and
B (2), two novel
indole alkaloids featuring unprecedented 6/5/6/6/5 and 6/5/5 cores,
together with seven known indole-linked 2,5-diketopiperazine alkaloids
(3–9), were isolated from the soil-derived
fungus Clonostachys rosea YRS-06. The new structures
were proposed through HR-MS, NMR, and ECD spectroscopic data. They
were established by comparing the calculated NMR, ECD, and specific
rotation data with the experimental. To assist in determining the
absolute configuration of the chiral carbon in the side chain of 2,5-diketopiperazine
derivatives, flexible analogues 3i–3iv were synthesized and analyzed. 1 was active against Fusarium oxysporum with an MIC value of 50 μg/mL. 7 and 8 showed excellent activity against human
HeLa and HepG2 cells with IC50 values of 0.12–0.60
μM.
Metrics & MoreArticle RecommendationsT he structure of clonorosin B (2) was elucidated incorrectly. The structure is as shown below. The specific rotation (+80.00) initially reported for 2 was an error due to an inadvertent switching of samples. The rotation for 2 is 0.00.The structure elucidation for the corrected structure of clonorosin B (2), calculated 13 C NMR shifts, and associated figures and tables are presented below. The authors apologize for any inconvenience.
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