Catalyzes the flavin-dependent Baeyer-Villiger oxidation of 1-deoxy-11-oxopentalenic acid to neopentalenolactone D in the biosynthesis of neopentalenolactone antibiotic. 1-deoxy-11-oxopentalenate + H(+) + NADPH + O2 = H2O + NADP(+) + neopentalenolactone D Binds 1 FAD per subunit. Antibiotic biosynthesis; neopentalenolactone biosynthesis. Cells lacking both ptlE and ptlD accumulate 1-deoxy-11-oxopentalenic acid. S.avermitilis does not produce pentalenolactone itself in vivo but instead a group of new metabolites that are neopentalenolactone derivatives. Belongs to the FAD-binding monooxygenase family.