Synthesis of Dysiherbaine Hatakeyama , Jerangolid D Marko and -Spirolaxine Me Ether Trost

Several new developments in enantioselective C-O ring construction have been applied in the s mtheses of natural products. To achieve control, the oxygenated quaternary center of dysiherbaine 9 must be established under kinetic conditions. One approach would be Sj 2 opening, but this would require displacement at a fully-substituted center. Susumi Hatakeyama of Nagasaki University has shown (Chem. Commun. 2007, 4158) that the epoxide 6, prepared by the Sharpless procedure, undergoes just such an opening under mild acid catalysis. 

The spiroketal (+)-spiroxaliiie methyl ether 31 contains three secondary oxygenated ste-reogenic centers. In a showcase of current chiral technology, Barry M. Trost of Stanford University constructed (Angew. Chetn. Int. Ed. 2007, 46, 7664) the first two of the three alcohols by the enantioselective addition of an aUsyne to an aldehyde. The chiral catalyst 25 that directed the alkyne additions was derived from a commercial Hgand. The last alcohol center was derived from / -(+)-epoxypropane. Note that the spiroketal was not prepared in the usual way, by acid-catalyzed cyclization of a dihydroxy ketone, but by Pd-catalyzed cyclization of the alkyne diol 30. 

Richard J. K. Taylor of the University of York has developed (Angew. Chem. Int. Ed. 2008, 47, 1935) the diasteroselective intramolecular Michael cyclization of phosphonates such as 2. Quenching of the cyclized product with paraformaldehyde delivered (+)-Paeonilactone B 3. 

Roberto Fernandez de la PradUla of the CSIC, Madrid established Tetrahedron Lett. 2008, 49, 4167) the diasteieoselective intramolecular hetero Michael addition of alcohols to enantiomericaUy-pure acychc sulfoxides such as 4 to give the aUylic sulfoxide 5. Mislow-Evans rearrangement converted 5 into 6, the enantiomericaUy-pure core of Ethyl Deoxymonate B 7. 

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Synthesis of Dysiherbaine (Hatakeyama), Jerangolid D (Marko) and (+)-Spirolaxine Me Ether (Trost)... 

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