Rose Bengal zinc oxide

Kondo et al. (182,183) reported a conversion of a fully aromatized phenolbetaine to a phthalide skeleton through photooxygenation. Reduction of norcoralyne (54) with zinc in acetic acid afforded dihydronorcoralyne (374), which was oxidized with m-chloroperbenzoic acid to the fully aromatized phenolbetaine 375 (Scheme 67). Photooxygenation of 375 in the presence of Rose Bengal, followed by reduction with sodium borohydride, gave rise directly to the phthalideisoquinoline 376 in 70% yield. The same phthalide (376) was also obtained from 2 -acetylpapaveraldine (129) (Section III,B,1). 

Photooxidation of alkaline phosphatase in the presence of methylene blue and Rose Bengal causes loss of activity for both native and apo-enzyme. In the case of the native enzyme, zinc protects 2 to 3 of the 16 histidine residues. The rate of oxidation of tryptophan is not affected by zinc, and there was no loss of tyrosine. Also, photooxidation of the apoenzyme diminishes zinc binding. It would appear that histidine residues play a role in binding the two zinc ions necessary for enzymic activity (91). 

Oxyberberine (49), when further oxidized by pyridine chlorochromate and then treated with methanol, gives the methoxy-ketone (50 R = Me) the tetra-methoxy-analogue of (49) behaves similarly.132 The carbinolamine (50 R = H) is obtainable, together with the keto-acid (53), by the photolysis of oxidoberberine (51), in the presence of oxygen and rose bengal, to produce the peroxide (52), followed by treatment with pyridine hydrochloride a tetramethoxy-analogue of oxidoberberine, prepared by the reduction of norcoralyne with zinc and acetic acid, followed by oxidation with a peracid, behaves in the same way.133... 

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