45 パラジウム触媒によるステロイド合成における立体制御(口頭発表の部)
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概要
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The regioselective palladium-catalyzed hydrogenolysis of allylic compounds with formic acid-triethylamine is applied to the stereocontrolled synthesis of steroid side chains and cis and trans ring junctions. The isopropenyl group is prepared from the C-17 keto steroid by isopropenylation, followed by hydrogenolysis. The C-20 allylic carbonates 3 and 5a,b in a steroid side chain are prepared from the C-20 keto steroid 1, and subjected to the palladium-catalyzed hydrogenolysis with formic acid-triethylamine at room temperature. The reaction proceeds regio- and stereoselectively, and both natural and unnatural configurations 6 and 7 at C-20 can be generated cleanly in high yields from the cis and trans allylic carbonates 3 and 5, respectively. The hydrogenolysis of C-3 allylic formate in A ring of a steroid is regioselective and stereospecific. The hydrogenolysis of α-allylic formate affords the cis ring junction. The trans ring junction is obtained by the hydrogenolysis of β-allylic formate. Mechanism of these regioselective and stereospecific reactions is discussed.
- 天然有機化合物討論会の論文
- 1992-09-10