Journal of the American Chemical Society p. 4114 - 4125 (1981)
Update date:2022-08-04
Topics:
Rollinson, Susan Wells
Amos, Richard A.
Katzenellenbogen, John A.
The total synthesis of obtusilactones (1a,b, 2a,b), mahubanolides (1c, 2c), epilitsenolides (5b, 6b), and dihydromahubanolides (4c, 5c, 6c) is described.The enolates derived from the α-phenylselenenyl esters (17a-c) were used as acrylate α-anion synthons; aldol addition to propargylaldehyde, followed by oxidation to the selenoxide and elimination, furnished the isomeric acetylenic esters 20a-c and 21a-c.In a similar manner, aldol addition to acrolein followed by oxidation/elimination yielded olefinic esters 18b,c and 19b,c.The acetylenic esters were saponified, and the corresponding carboxylic acids were converted by either mercuric ion-catalyzed or bicarbonate-catalyzed lactonization to the obtusilactones (1a,b, 2a,b) and mahubanolides (1c, 2c).The olefinic esters were saponified, and the corresponding carboxylic acids lactonized to γ-substituted lactones (30b,c, 32b,c 32c) by treatment with either phenylselenenyl chloride or iodine.The epilitsenolides (5b, 6b) and dihydromahubanolides (5c, 6c) were then obtained by treating the substituted γ-lactones with tri-n-butyltin hydride.Homogeneous catalytic hydrogenation (Rh(PPh3)3Cl) of isomahubanolide (2c) gave a mixture of dihydromahubanolides 4c and 6c.
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