Novel Regio- and Stereoselective Cascade 6-endo-trig Cyclisations from Polyene Acyl Radical Intermediates Leading to Steroid-Like Pentacycles and Heptacycles
作者:Sandeep Handa、Prathap S. Nair、Gerald Pattenden
DOI:10.1002/1522-2675(20000906)83:9<2629::aid-hlca2629>3.0.co;2-w
日期:2000.9.6
In a quite remarkable regio- and stereoselective manner, each of the (all-E)-polyene selenoates 5a-c is shown to undergo cascade radical-mediated polycyclisations via consecutive 6-endo-trig reactions, leading to the corresponding all-trans, anti, tri-, penta- and heptacycles, i.e., 20, 23, and 25, in good yields. The configurations of these 'steroid-like' polycycles followed from detailed examination and correlation of chemical shift data in their C-13-NMR spectra.