Aromatic and aliphatic hydroxylations as well as U-demethylations occurred during metabolism of aromatic substrates by a range of fungi. para-Hydroxylation of monosubstituted aryl rings by fungi proceeded with migration and retention of deuterium label (NIH shift) and appeared to involve onlyarene 3.4-oxide intermediates, in common with plant and animal metabolism. The possibility of contributions from arene 1.2-or 2.3-oxide intermediates during orrho-hydroxylation is examined in the light of the results of oxygen-18 incorporation, the lack of deuterium-hydrogen primary kinetic isotope effects, and the wide range of deuterium migration and retention values. From these last experimental data no evidence for an arene oxide isomerase enzyme w a s found. istry, Queen'
Rates of E-Z isomerization in N-alkylimines have been determined by direct thermal stereomutation and by dynamic n.m.r. spectroscopy. Thermal racemization rates of optically active para-disubstituted 2-t-butyl-3.3-diphenyloxaziridines have also been measured, and show a small but consistent correlation with Hammett op. Comparison of the activation parameters for imine isomerization with data for nitrogen inversion in oxaziridines indicates that Nalkylimines isomerize by a planar inversion (lateral shift) mechanism. Barriers determined for an aldimine under optimal conditions are higher than previously reported for imines (ca. 30 kcal mol-l).
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