Syntheses of new hydroxy-[3.3]orthocyclophanes as models for the galactose oxidase Tyr-Cys cofactor

The syntheses of 3,4-benzo-8,9-(3′-hydroxybenzo)bicyclo[4,4,1]undeca-3,8-dien-11-one, 3,4-benzo-8,9-(3′-hydroxy-4′-methylsulfanylbenzo)bicyclo[4,4,1]undeca-3,8-dien-11-one and their ethylene acetals have been achieved. Crystallographic, UV/Vis and NMR data show that the two ketones adopt boat/chair conformations that are fluxional in solution, while the acetals exhibit chair/chair conformations with layered benzo rings. Comparison of the oxidation potentials of the four compounds suggests that an ortho-methylsulfanyl substituent and a π–π interaction both thermodynamically stabilise the phenoxonium radical species derived from these compounds, by approximately equal amounts.