Diosphenol synthesis

Several routes to 2,3-diketones have been reported. The most practical and general method is that of Ruzicka, Plattner and Furrer as adapted by Nace and Nelander for synthesis of the diosphenol corresponding to 5a-pregnane-2,3,20-trione (44) starting from 5a-pregnane-3,20-dione (40). The overall yield of diosphenol (44) by this route is 62% based on... 

Schneider, D.E, and Viljoen, M.S., Synthesis of annulated 4-alkylidenebutenohdes from natural occurring diosphenols, Synth. Commun., 21, 3349, 1997. 

The formation of the diosphenol (214) from pachysandrine-A is an interesting reaction. ON-Deacylpachysandrine-A was oxidised (chromic acid) to the ketone (213). Treatment of this ketone with 5% ethanolic KOH gave the diosphenol (214), which is an intermediate used in the synthesis of the pachysandrines and epipachysandrine-A. ... 

Epipachysandrine-A is a new alkaloid to which the formula (218) " has been assigned. Its synthesis from the diosphenol (214) is described below. On hydrolysis and iV-methylation, (218) is converted into 3/5,20a-bisdimethylamino-4)8-hydroxy-5a-pregnane (219). 

The synthesis is strongly impacted by the following decomposition reactions On the one hand, under the influence of strong acids or bases, astaxanthin gives products with a diosphenol structure. On the other hand, astaxanthin is sensitive to oxidation and thereby a,)S-unsaturated 1,2-diketones (i.e. semiastacene and astacene) are readily formed. 

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