Cytochrome P450 that catalyzes an intramolecular para-para' C-C phenol coupling of 4'-O-methylnorbelladine in alkaloids biosynthesis, including haemanthamine- and crinamine-type alkaloids, promising anticancer agents. Catalyzes the formation of (10bR,4aS)-noroxomaritidine and (10bS,4aR)-noroxomaritidine from 4'-O-methylnorbelladine. Produces also N-demethylnarwedine as a minor product. Involved in the biosynthesis of haemanthamine. Can use also 4'-O-methyl-N-methylnorbelladine, (S)- and (R)-coclaurine as substrates, but not 3'-O-methylnorbelladine, 3',4'-O-dimethylnorbelladine, norbelladine, haemanthamine, (10bS,4aR)- or (10bR,4aS)-noroxomaritidine, isovanillin or tyramine. 4'-O-methylnorbelladine + O2 + reduced [NADPH--hemoprotein reductase] = (10bS,4aR)-noroxomaritidine + H(+) + 2 H2O + oxidized [NADPH--hemoprotein reductase] 4'-O-methylnorbelladine + O2 + reduced [NADPH--hemoprotein reductase] = (10bR,4aS)-noroxomaritidine + H(+) + 2 H2O + oxidized [NADPH--hemoprotein reductase] kcat is 15.0 min(-1) with 4'-O-methylnorbelladine as substrate. kcat is 2.44 min(-1) with 4'-O-methyl-N-methylnorbelladine as substrate. kcat is 1.34 min(-1) with (S)-coclaurine as substrate. kcat is 2.07 min(-1) with (R)-coclaurine as substrate. Optimum pH is 6.5. Optimum temperature is 30 degrees Celsius. Alkaloid biosynthesis. Belongs to the cytochrome P450 family.