Dactylides D and E, two modified 22-membered polyol macrolides isolated from Dactylosporangium aurantiacum.

Two new 22-membered macrolides, dactylide D (1) and dactylide E (2), featuring substituted amino acid or a contiguous dipropionate unit, along with the known dactylosporolide B (3), were purified from Dactylosporangium aurantiacum ATCC 23491. Their structures were determined through comprehensive spectroscopic analysis and comparison with related congeners. Compound 1 features an N-acetylalanyl side chain, while compound 2 bears an unusual (E)-7-amino-oxohept-5-enoic acid moiety, along with C-7 oxidation and loss of the tetrahydropyran ring. NOE correlations indicated that the stereochemistry of the macrolactone cores in 1 and 2 is conserved relative to dactylide B. These findings expand the structural diversity of polyol macrolides from D. aurantiacum, underscoring the strain's potential for natural product discovery.