Discovery of Hypoiodite-Mediated Aminyl Radical Cyclization Lacking a Nitrogen Radical-Stabilizing Group: Application to Synthesis of an Oxazaspiroketal-Containing Cephalostatin Analog
摘要:
Synthesis of an oxazaspiroketal-containing bissteroidal pyrazine is described. The key transformation of this synthesis involves stereoselective formation of oxazaspiroketal via aminyl-radical cyclization of primary amine lacking a radical-stabilizing group by Suarez hypoiodite oxidation.
Ruthenium-Catalyzed Mild C−H Oxyfunctionalization of Cyclic Steroidal Ethers<sup>1</sup>
作者:Jong Seok Lee、Hui Cao、Philip L. Fuchs
DOI:10.1021/jo070382s
日期:2007.7.1
Ruthenium-catalyzed site-specific C−H oxyfunctionalization of steroidal ethers with periodate or bromate as terminal oxidants in phosphate buffer provided the acid-sensitive C-16 hydroxy compounds in high yields. Phosphate buffer (pH 7.5) significantly inhibits formation of unwanted side products generated under more acidic reaction conditions. A key example is demonstrated at the 100 g scale.
Redox Refunctionalization of Steroid Spiroketals. Structure Correction of Ritterazine M
作者:Seongmin Lee、Thomas G. LaCour、Douglas Lantrip、Philip L. Fuchs
DOI:10.1021/ol0165894
日期:2002.2.1
The structure of the North spiroketal moiety of ritterazine M has been corrected from 1a to 1b. This was accomplished by comparison of published spectra of the natural product with five synthetic spiroketal-alcohols. Synthesis of these models was efficiently accomplished by reductive cleavage of the spiroketal and Sharpless asymmetricdihydroxylation of an isopentyl, methyl 1,1-disubstituted olefin
An Efficient C−H Oxidation Protocol for α-Hydroxylation of Cyclic Steroidal Ethers
作者:Seongmin Lee、Philip L. Fuchs
DOI:10.1021/ol049712a
日期:2004.4.1
Various C-16 hydroxy steroids have been prepared with the aid of CrO3/Bu4NIO4. Out of the two possible reaction courses, transition state B is favored because of less steric interference between substrate and CrO4. Thus, C-H bonds at C-16 are oxidized selectively.