Synthesis of natural maleimides farinomaleins C–E and evaluation of their antifungal activity

A practical and convenient synthesis of naturally occurring farinomaleins C–E was achieved starting from readily available ethyl 3-methyl-2-oxobutyrate and triethyl phosphonoacetate. The key steps of the sequence included a Horner–Wadsworth–Emmons condensation to obtain the precursor farinomalein A and coupling with suitable alcohols to install the chain. The synthesis of farinomalein D has been achieved starting from (R)-isopropylideneglycerol on the basis of which the S configuration was assigned to the natural compound. The antifungal activity of the synthesized compounds was evaluated against Cladosporium cladosporioides.