In situ nitrosonium ion generation — α-Oximinylation of enol ethers from steroidal spiroketals: Introduction of C23 (R)-OH in cephalostatin intermediates
Synthesis of C14,15-Dihydro-C22,25-<i>epi</i> North Unit of Cephalostatin 1 via “Red-Ox” Modifications of Hecogenin Acetate
作者:Seongmin Lee、Daniel Jamieson、Philip L. Fuchs
DOI:10.1021/ol802122p
日期:2009.1.1
The C14,15-Dihydro-C22,25-epi north unit of cephalostatin1 has been synthesized in 11 operations from commercially available hecogenin acetate via multiple reductions and oxidations. The key transformations include (i) CrVI-catalyzed E-ring opening, (ii) C17 hydroxylation, and (iii) a base-triggered cyclization cascade.
An Assisted Solvolysis of 23-Spirostanyl Bromides and Tosylates. A New Rearrangement of Spirostanes to the Bisfuran Systems
作者:Romana Anulewicz-Ostrowska、Izabella Jastrzȩbska、Jacek W. Morzycki、Jacek Wójcik
DOI:10.1021/jo020231j
日期:2002.10.1
Steroidalsapogenins bearing a good leaving group at C23 undergo a completely stereospecific rearrangement under a variety of conditions via a mechanism involving neighboring-group participation by the acetal oxygen atom in the departure of the nucleofuge from C23. The reactions of equatorial (23S)-23-bromo- or (23S)-23-tosyloxyspirostanes with either the alpha (25R) or beta (25S) oriented 25-methyl