Methylenedioxy bridge-forming cytochrome P450 involved in the biosynthesis of isoquinoline alkaloids. Converts (R,S)-cheilanthifoline to (S)-stylopine with a high substrate specificity. Catalyzes an oxidative reaction that does not incorporate oxygen into the product. (S)-cheilanthifoline + O2 + reduced [NADPH--hemoprotein reductase] = (S)-stylopine + H(+) + 2 H2O + oxidized [NADPH--hemoprotein reductase] Alkaloid biosynthesis. Expressed in roots and at lower levels in stems and leaves. Up-regulated by methyl jasmonate treatment. Belongs to the cytochrome P450 family.