Shivaji B. Markad, N. Argade
Jan 5, 2018
Citations
0
Influential Citations
13
Citations
Journal
The Journal of organic chemistry
Abstract
Starting from dimethyl (E)-2-{[(1-tert-butoxycarbonyl)-1H-indol-3-yl]methylene}succinate and (R)-2,2,5,5-tetramethyl-1,3-dioxolane-4-carbaldehyde, facile synthesis of (-)-epi-claulansine D was accomplished via condensation and two intramolecular cyclizations. The (-)-epi-claulansine D in the solid state exists in a metastable form, and after an induction period of 30-90 days, it underwent complete epimerization to exclusively deliver the desired natural product (-)-claulansine D in quantitative yield. The witnessed inversion of C-centrochirality in the solid state is conceptually novel and takes place for relatively higher crystal stability reasons. Base-catalyzed ring expansion of both (±)/(-)-epi-claulansine D and (±)/(-)-claulansine D resulted in (±)/(+)-epi-claulansine C in very good yields.