A Lewis Acid Mediated StereoselectiveRemoval of an Anomeric Urea Substituent
作者:Richard P. Hsung、Craig R. Berry、C. Rameshkumar、Michael R. Tracey、Lin-Li Wei
DOI:10.1055/s-2003-38747
日期:——
The first Lewisacidmediated stereoselective removal of an anomeric chiral urea group or an electron deficient nitrogen substituent is described here. The ability to remove this urea group which had served as a chiral auxiliary, along with stereoselective hydroboration-oxidation of the endocyclic olefin renders the pyranyl cycloadduct from hetero [4+2] cycloadditions of chiral allenamides a useful
A Formal Total Synthesis of (+)-Zincophorin. Observation of an Unusual Urea-Directed Stork−Crabtree Hydrogenation
作者:Zhenlei Song、Richard P. Hsung
DOI:10.1021/ol070791a
日期:2007.5.1
A formal total synthesis of (+)-zincophorin via interception of Miyashita's advanced intermediates is described here. This effort features the first synthetic application of an inverse demand hetero [4 + 2] cycloaddition of a chiral allenamide, and the observation of an unusual urea directed Stork-Crabtree hydrogenation.
Studies on a Urea-Directed Stork−Crabtree Hydrogenation. Synthesis of the C1−C9 Subunit of (+)-Zincophorin
作者:Zhenlei Song、Richard P. Hsung、Ting Lu、Andrew G. Lohse
DOI:10.1021/jo7017922
日期:2007.12.1
[GRAPHICS]A detailed account on the stereoselective synthesis of the C1-C9 subunit of (+)-zincophorin is described here. This approach features the first application of a stereoselective inverse electron demand hetero-[4 + 2] cycloaddition of chiral allenamides in natural product synthesis. The C1-C9 subunit matches Cossy's intermediate, thereby constituting a formal total synthesis. In addition, details of an unusual urea-directed Stork-Crabtree hydrogenation observed during these efforts are also disclosed here.