Antibiotics from Gliding Bacteria, LIV. Isolation and Structure Elucidation of Soraphen A1α, a Novel Antifungal Macrolide from Sorangium cellulosum†
From the myxobacterium Sorangium cellulosum, strain So ce26, a novel group of highly active antifungal metabolites was isolated. Large-scale production of the basic compound soraphen A1α (1) was achieved by fermentation in the presence of the adsorber resin XAD-16, extraction and crystallization. The 18-membered macrolide structure of 1 was determined by spectroscopic methods. X-ray crystal structure analysis revealed the absolute configuration of the ten asymmetric centers. According to proton coupling constants and difference NOE measurements the solution conformation in CDCl3 and [D6]DMSO is very similar to that in the crystal structure.