Stereodivergent Approach to Both C2,8a-syn and C2,8a-anti Relative Stereochemical Manifolds in the Lepadin Family via a TiCl4-Promoted Aza-[3+3] Annulation
Stereodivergent Approach to Both C2,8a-syn and C2,8a-anti Relative Stereochemical Manifolds in the Lepadin Family via a TiCl4-Promoted Aza-[3+3] Annulation
作者:Gang Li、Richard P. Hsung、Brian W. Slafer、Irina K. Sagamanova
DOI:10.1021/ol802068q
日期:2008.11.6
An enantioselective total synthesis of (+)-lepadin F is described. The synthetic sequence features an intermolecular aza-[3 + 3] annulation, homologation of a vinylogous amide via Eschenmoser's episulfide contraction, and a highly stereoselective hydrogenation essential for achieving the 1,3-anti relative stereochemistry at C2 and C8a.
Stereoselective <i>trans-</i> and <i>cis-</i>Dihydroxylations of 2<i>H</i>-Pyranyl and Dihydropyridinyl Heterocycles Synthesized from Formal [3 + 3]-Cycloaddition Reactions of α,β-Unsaturated Iminium Ions with 1,3-Dicarbonyl Equivalents<sup>†</sup>
作者:Luke R. Zehnder、Lin-Li Wei、Richard P. Hsung、Kevin P. Cole、Michael J. McLaughlin、Hong C. Shen、Heather M. Sklenicka、Jiashi Wang、Craig A. Zificsak
DOI:10.1021/ol010034r
日期:2001.7.1
[GRAPHICS]We describe here an inherent problem in direct epoxidation of the endocyclic olefin in 2H-pyrans fused to 2-pyrones, Such difficulties led to the development of highly stereoselective trans- and cis-dihydroxylations of these olefinic systems in both 2H-pyrans and dihydropyridines fused to a 2-pyrones or a 2-cyclohexenone. Protocols for the removal of the activated allylic hydroxyl group are also reported.