sets of results give information about the mechanism of carbonyl activation by (S)-proline during asymmetricsyntheses: (i) X-ray structures of two ketols produced by the proline-induced cyclization of triketones; (ii) (S)-Proline-catalyzed asymmetric dehydration of (±)-β ketols leading to opticallyactive enones.
Total Synthesis of Neohedycaryol. Its Possible Role in the Biosynthesis of Eudesmane Sesquiterpenes
作者:Adriaan J. Minnaard、Gerrit A. Stork、Joannes B. P. A. Wijnberg、Aede de Groot
DOI:10.1021/jo962056a
日期:1997.4.1
the germacrane sesquiterpene hedycaryol, was accomplished in 10 steps from the known dione 6. A Marshall fragmentation of the intermediate mesylate 14 was used to prepare the trans,trans-cyclodeca-1,6-diene ring present in neohedycaryol. During the synthesis of 14, a pronounced example of through-bondinteractions (TBI) was observed. The preferred elongated chair conformation of neohedycaryol was demonstrated
Herein, we describe a catalytic asymmetric intramolecular vinylogous aldolreaction by taking advantage of dual organocatalysts, which enables convergent synthesis of ortho-fused tricyclic diketones in excellent enantioselectivities and diastereoselectivities. Noteworthy is that the reaction stereoselectively forges three consecutive stereogenic carbon centers including a quaternary one. Density functional