Novel degradation products from the treatment of salinomycin and narasin with formic acid.

Salinomycin and narasin (4-methylsalinomycin) upon treatment with HCO2H furnish the known furanone fragment 3 and the complementary but rearranged fragments 1 and 2 respectively. The structure of 1 has been established by X-ray analysis. Upon being heated under reflux in PhMe, 1 undergoes the retrograde aldol reaction to furnish alpha, gamma-dimethyl-2-furanbutanal (4). The furan moiety of 1 is more resistant to electrophilic substitution than expected, but it can be acylated by highly reactive reagents such as (CF3CO)2O and AcOSO2Me. Compounds 1 and 2, the acetyl and trifluoracetyl derivatives of the former, and the reduction products thereof have no significant anticoccidial activity.