Catellatolactams A–C (1–3), three novel ansamacrolactams, were isolated from the culture
extract
of an underexplored rare actinomycete of the genus Catellatospora. Spectroscopic and spectrometric analyses by NMR and MS elucidated
the structure of 1 to be a lactamized pentaketide presumably
extended on a 3-amino-5-hydroxybenzoic acid starter unit. Compounds 2 and 3 further received epoxidation and intramolecular
cross-linking to incorporate a 2-indolinone unit, with a 3-amino-5-hydroxybenzoic
acid pendant on 3. The absolute configurations of 2 and 3 were unequivocally established to both
be 2S,6R,7R by
comparison of the experimental NMR chemical shifts and ECD spectra
with those predicted by DFT-based quantum chemical calculation. While 1–3 showed no appreciable antimicrobial
activity or cytotoxicity, root elongation of germinated lettuce seeds
was promoted by 2 and 3 at 1–10 μM.
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