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Structure-activity studies of irumamycin type macrolides from Streptomyces sp. INA-Ac-5812
Three natural glycosylated macrolide compounds, known irumamycin 1 and X-14952B 2, as well as new
isoirumamycin 3, were isolated from ethyl acetate mycelium extract of Streptomyces sp. INA-Ac-5812.
Structures of the compounds were elucidated using 1D and 2D NMR. Isoirumamycin 3 was found to
be an isomer of irumamycin with an 18-membered macrolactone ring instead of 20-membered macrolide
in irumamycin. A previously unknown stereo configuration of irumamycin epoxide (C23, C24) and
hemiketal (C3, C7) fragments was deduced from NMR data (ROESY/NOESY and HSQMBC). Cytotoxic, antifungal
and antibacterial activities were studied for all isolated compounds. Comparison of the collected
data showed crucial importance of 20-membered macrolactone ring for antimicrobial properties of this
antibiotic family.