Studies on the biosynthesis of 2-hydroxy-1,4-benzoxazin-3-one (HBOA) from 3-hydroxyindolin-2-one in Zea mays

The ring expansion of 3-hydroxyindolin-2-one to 2-hydroxy-l,4-benzoxazin-3-one (HBOA) was investigated by labelling experiments. Action of the cytochrome P450 enzyme BX4 from maize on 3-hydroxyindolin-2-onc under an O-18(2) atmosphere induced production of 2-hydroxy-1.4-benzoxazin-3-one in which the ring oxygen - but not the 2-hydroxy group of HBOA - is labelled. A mechanism fur this transformation is proposed, (C) 2001 Elsevier Science Ltd. All rights reserved.