Perhydrohistrionicotoxin, Barton nitrite

The Barton reaction was utilized during the synthesis of various terpenes and has played a crucial role in the elucidation of terpene structures. The Barton nitrite ester reaction was a key step in E.J. Corey s synthesis of azadiradione and perhydrohistrionicotoxin . Even though the yields were low, other ways to access the same intermediates would have been tedious, and afforded lower overall yields than in the applied Barton reactions. 

The Barton nitrite photolysis reaction also had an important role in terpene synthesis and the elucidation of terpene stmcture. For example, in Corey s syntheses of azadiradione and perhydrohistrionicotoxin " selective functionalization by means of the nitrite photolysis reaction was the crucial... 

Other important applications of Barton reaction are in the synthesis of alkaloids and terpenoids. For example, the photolysis of nitrite 6 was used in a crucial step in the synthesis of alkaloid perhydrohistrionicotoxin 7 [6]. The oxime 8, formed in about 20 % yield, gives the spirolactam ring of the alkaloid 7 on Beckmann rearrangement. 

Remote Oxidation.—Remote oxidation reactions generally involve intramolecular hydrogen abstraction. The best known example is the Barton reaction (photolysis of nitrite esters). "- One of the most important applications of this reaction was to the synthesis of aldosterone acetate. The yield of this reaction has been substantially improved (55%) by irradiating the dienone nitrite ester (172) in which the extended conjugation ensures that sufficient separation between C-19 and the 11/3-oxygen atom exists to suppress functionalization at C-19 in favour of attack at C-18. Another recent application of the Barton reaction occurred in the synthesis of perhydrohistrionicotoxin (175), where the key step was the stereoselective formation of the oxime (174) from the nitrite ester (173). °... 

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