4a,5-Cycloaddiction reactions of acetylenic compounds at the flavoquinone nucleus as mechanisms of flavoprotein inhibitions.

Photochemically, covalent cycloaddition products of flavoquinone and acetylenic enzyme inhibitors have been prepared and elucidated, which appear analogous to flavoprotein-inhibitor complexes (monoamine and lactate oxidase). The additions occur with inhibitors of general type H C = C — C H < at the C (4a )=N(5 ) azomethine grouping of oxidized flavin. The spectral properties of adducts and their chemical reactivity is described.