Nine new pentacyclic polyketides, fasamycins G−K (1−5) and formicamycins N−Q (6−9), along with 10 known analogues (10−19), were isolated from a rhizospheric soil-derived Streptomyces sp. KIB-1414. Their structures and absolute configurations were elucidated by interpretation of NMR and HRMS data and comparisons of CD data. The compounds were active against methicillin-resistant Staphylococcus aureus (MRSA), Staphylococcus aureus, Bacillus subtilis, and Escherichia coli strains, with MIC values ranging from 0.20 to 50.00 μg/mL.
Quinolizidomycins A (1) and B (2), two
unprecedented quinolizidine alkaloids featuring a tricyclic 6/6/5
ring system, were isolated from Streptomyces sp.
KIB-1714. Their structures were assigned by detailed spectroscopic
data analyses and X-ray diffraction. Stable isotope labeling experiments
suggested that compounds 1 and 2 are derived
from lysine, ribose 5-phosphate, and acetate units, which indicates
an unprecedented manner of assembly of the quinolizidine (1-azabicyclo[4.4.0]decane)
scaffold in quinolizidomycin biosynthesis. Quinolizidomycin A (1) was active in an acetylcholinesterase inhibitory assay.
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