1H and 13C assignments of two new macrocyclic lactones isolated from Streptomyces sp. 211726 and revised assignments of Azalomycins F3a, F4aand F5a

Azalomycin F4a 2‐ethylpentyl ester (1) and Azalomycin F5a 2‐ethylpentyl ester (2), two new macrocyclic lactones, along with three known compounds of Azalomycins F3a (3), F4a (4) and F5a (5), were identified from metabolites of Streptomyces sp. 211726 isolated from mangrove rhizosphere soil. The complete 1H and 13C assignments of these compounds were achieved by using 1H, 13C, DEPT, HSQC, 1H‐1H COSY and HMBC spectra, and the relative stereochemistry of 5 was first elucidated on the basis of proton–proton coupling constants, NOESY and IR spectra. Moreover, some errors in the 1H and 13C assignments published of 3, 4 and 5 were found and revised. 1 and 2 were active against Candida albicans, and exhibited moderate cyctotoxicity against HCT‐116 cell line. Copyright © 2010 John Wiley & Sons, Ltd.