H-1 and C-13 assignments of two new macrocyclic lactones isolated from Streptomyces sp 211726 and revised assignments of Azalomycins F-3a, F-4a and F-5a

Azalomycin F-4a 2-ethylpentyl ester (1) and Azalomycin F-5a 2-ethylpentyl ester (2), two new macrocyclic lactones, along with three known compounds of Azalomycins F-3a (3), F-4a (4) and F-5a (5), were identified from metabolites of Streptomyces sp. 211726 isolated from mangrove rhizosphere soil. The complete H-1 and C-13 assignments of these compounds were achieved by using H-1, C-13, DEPT, HSQC, H-1-H-1 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 H-1 and C-13 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 (C) 2010 John Wiley & Sons, Ltd.