Corticosteroids sodium bismuthate

Selective oxidative cleavage of the corticosteroid side chain by sodium bismuthate was used as an analytical technique for the determination of urinary corticosteroids. Sodium bismuthate was chosen since it cleaves a-hydroxy acids readily (unlike periodic acid) and tolerates the water in urine samples (in contrast to LTA). 

System (2) has been described for the assay of corticosteroids (cortisone, hydrocortisone, prednisone, and prednisolone) in urine [141]. Prior to introduction into the GC system, the sample was eluted with 2 1 ethyl acetate-methanol, the extracts evaporated to dryness, and then oxidized with sodium bismuthate. Used in the method was a silanized column (132 cm X 5 mm) containing 2,2-dimethylpropane-l,3-diol adipate (0.65%) supported on celite, and operated at 230°C. The carrier gas was argon, and the detector used strontium 90-ionization. The standard deviation was 3.5 % (based on 47 determinations). 

Scheme 5.2. Selective oxidative cleavage of corticosteroid side chains with sodium bismuthate [53BJ371].

The synthesis of a topical anti-inflammatory, anti-allergic agent that is inactivated in the bloodstream starts with the scission of the dihydroxyacetone side chain of the corticosteroid fluoroprednisolone (34-1) (see Chapter 7, Scheme 7.17) with sodium bismuthate (Scheme 5.34). Reaction of the product, 34-2, with methanethiol affords the thioacetal 34-3. The acetal extrudes one of the thiomethyl groups under acidic conditions to form the enol thioether 34-4. Treatment of that product with ethanethiol restores the thioacetal (34-5). The stereochemistry at Cu is defined by addition of ethanethiol from the more open backside of the thioenol 34-4. 

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