Teubrevin G and Teubrevin H: The First Total Syntheses of Rearranged <i>n</i><i>eo</i>-Clerodanes Including Solutions to the Problems of Chirality Merger and Furan Ring Assembly
作者:Leo A. Paquette、Ivan Efremov
DOI:10.1021/ja010313+
日期:2001.5.1
of a 1,3-dimesityl-4,5-dihydroimidazol-2-ylideneruthenium precatalyst. The key building blocks 39 and 48 were constructed by asymmetric processes and coupled under conditions where good remoteasymmetricinduction was realized. The diastereoselection observed in this alkylation reaction appears to be intimately associated with the conformational properties of the beta-keto ester enolate. While the readily
Carbonyl compounds 1 were converted to the corresponding 1,3-dioxolanes 2 and 1,3-dioxanes 4 with ethylene glycol and 2,2-dimethyl-1,3-propandiol, respectively, in the presence of 1-3 mol% of N-(benzyl, 4-methylbenzyl or 4-methoxybenzyl)-2(or -4)-cyanopyridinium hexafluoroantimonates 3. The catalyst 3d was also effective for the tetrahydropyranylation.