Selection of a specifically blocked mutant of Streptomyces cinnamonensis: isolation and synthesis of 26-deoxymonensin A.

Streptomyces cinnamonensis produces the polyether ionophore antibiotic monensin A. Following a single round of mutagenesis by UV light, a derivative of this strain has been isolated, which secretes a new metabolite identified as 26-deoxymonensin A (3). The structural elucidation of the new metabolite followed from a spectroscopic analysis, and its identity was proven conclusively following a comparison to 26-deoxymonensin A (3) obtained synthetically from monensin A. The preparation of labelled forms of 3 is described, together with incorporation experiments using the parent strain of S. cinnamonensis. Only very low levels of incorporation of 3 into monensin A were observed.