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Fermentation of ATCC 74256 led to the isolation and identification of C7 ep
imers of phomoidride A (CP-225,917) and phomoidride B (CP-263,114). We sugg
est the names phomoidrides C and D for these new fermentation products, Stu
dies on the effect of pH on the distribution of phomoidrides A-D suggest ph
omoidride B (CP-263,114) is the first-formed secondary metabolite and the s
ource of the remaining three phomoidrides.