Total Synthesis of Viridiofungins A and B.

The total synthesis of viridiofungins A (1) and B (2) via β-lactone 3 in 13 steps is reported. Key steps included an HF-mediated rearrangement of cyclobutene diester 9 to form a bicyclic lactone 6, an olefin cross metathesis between disubstituted alkene 3 and alkene 4 in which isomerization was suppressed, and a novel β-lactone ring opening to form the amide. Deprotection then gave either viridiofungin A (1) or B (2) in high yield.