Fig. 24.

Baeyer-Villiger oxygenases act via Fl-4a-OO⁻ as nucleophile: (a) schematic for oxygen insertion into cyclohexanone with ring expansion to the 7 member lactone; (b) conversion of the tetracyclic scaffold of premithramycin B to the tricyclic scaffold of mithramycin DK starts with a Baeyer-Villiger ring expansion of ketone to lactone, followed by lactone hydrolysis and β-keto acid decarboxylation; (c) conversion of angucycline framework to twisted spiroketal in griseorhodin involves flavoprotein catalysis and can be formulated to involve Baeyer-Villiger enzymology; (d) Baeyer-Villigerase generation of neo-pentalenolactone D.