Rapid and Enantioselective Synthetic Approaches to Germanicol and Other Pentacyclic Triterpenes
作者:Karavadhi Surendra、E. J. Corey
DOI:10.1021/ja802730a
日期:2008.7.1
routes to the key intermediate 2 for the synthesis of the pentacyclic triterpene germanicol 1 have been developed. In the first, the ( S)-epoxide of farnesyl bromide is transformed in just three steps to the tetracyclic intermediate 7, which is converted to chiral 2 by treatment with polyphosphoric acid. The second synthetic route to 2 involves the coupling of the ( S)-epoxide 8 with vinyl iodide 9 to give
An Exceptionally Short and Simple Enantioselective Total Synthesis of Pentacyclic Triterpenes of the β-Amyrin Family
作者:Alan X. Huang、Zhaoming Xiong、E. J. Corey
DOI:10.1021/ja992411p
日期:1999.11.1
A new and very direct enantioselective total synthesis of members of the β-amyrin family of pentacyclic triterpenes has been developed starting with acylsilane 5, 2-propenyllithium, and cyclohexenylmethyl bromide 6, which were assembled to form tetraene 7. Cationic cyclization of 7 and silylation afforded 8, which after vinyl triflate formation was cyclized via a Cu(I) intermediate (Scheme 2) to form
Simple Enantioselective Approach to Synthetic Limonoids
作者:Douglas C. Behenna、E. J. Corey
DOI:10.1021/ja802376g
日期:2008.5.1
enantioselective and short approach to the synthesis of limonoids has been applied successfully to the simplest limonoid, 2. The carbon atoms of the tetracyclic framework were assembled in a single operation from the acylsilane 3 and the acetylenic sulfone 4 to form the chiral epoxide 5. Successive cationic and free-radical cyclizations starting with 5 generated the tetracyclic intermediates 9a, which was transformed