β-Tricarbonyl compounds. Part 1. Synthesis of the antibiotics uliginosin A, dihydrouliginosin B, and analogues thereof

The antibiotic uliginosin A-iBiB has been synthesised by a rottlerone exchange between albaspidin-iBiB and 2′,4′,6′-trihydroxy-3′-(3-methylbut-2-enyl)isobutyrophenone. Natural uliginosin A contains a homologue (M+ 14) and so analogues, in which each of the isobutyryl groups in uliginosin A is replaced by isovaleryl, have been prepared; uliginosin A-iViB is probably the minor component in natural uliginosin A. Dihydrouliginosin B-iBiB and isodihydrouliginosin B-iBiB have also been prepared.