Aldgamycins J–O, 16-Membered Macrolides with a Branched Octose Unit from Streptomycetes sp. and Their Antibacterial Activities

Six new 16-membered macrolides with a rare branched octose unit, aldgamycins J–O (1–6), along with two known compounds, swalpamycin B (7) and chalcomycin (8), were isolated from Streptomyces sp. HK-2006-1. Their structures were determined by detailed spectroscopic and X-ray crystallographic analysis. Natural products containing branched sugar units are rare. Aldgaropyranose and decarboxylated aldgaropyranose are branched octoses, specifically aldgarose-type branched octose. Until now, only 11 compounds have been reported to contain an aldgarose-type branched octose. The discovery of aldgamycins J–O (1–6) adds new members of this type of natural product. All the compounds (1–8) herein were tested for antimicrobial activities against Gram-positive Staphylococcus aureus 209P, Gram-negative Escherichia coli ATCC0111, and two fungi, Candida albicans FIM709 and Aspergillus niger R330. Most of these compounds showed antibacterial activity against S. aureus. Their preliminary structure–activity relationships are proposed.