Enantioselective Total Syntheses of (+)-Castanospermine, (+)-6-Epicastanospermine, (+)-Australine, and (+)-3-Epiaustraline
作者:Scott E. Denmark、Esther A. Martinborough
DOI:10.1021/ja9829970
日期:1999.4.1
The total syntheses of the potent glycosidase inhibitors castanospermine ((+)-1), 6-epicastanospermine ((+)-2), australine ((+)-3), and 3-epiaustraline ((+)-4) are described. The syntheses of indolizidine alkaloids (+)-1 and (+)-2 were accomplished in eight steps and in 18% and 24% overall yields from 2,5-dihydrofuran while the pyrrolizidine alkaloids (+)-3 and (+)-4 were obtained in a nine-step sequence
(+)-1-epiaustraline ((+)-1), a tetrahydroxypyrrolizidine alkaloid of the alexine/australine subclass, is described. The key step is a tandem intramolecular [4 + 2]/intermolecular [3 + 2] nitroalkenecycloaddition involving dienylsilyloxy nitroalkene3 and chiral vinyl ether 4, which establishes four of the five stereocenters present. The final center was installed by a diastereoselective dihydroxylation
Tandem [4 + 2]/[3 + 2] Cycloadditions of Nitroalkenes. 13. The Synthesis of (−)-Detoxinine
作者:Scott E. Denmark、Alexander R. Hurd、Hubert J. Sacha
DOI:10.1021/jo962306n
日期:1997.3.1
(-)-Detoxinine, an unusual, highly-functionalized amino acid, is the core residue of many components that comprise the detoxin complex. The synthesis of(-)-detoxinine was accomplished in 10 steps and 13.4% overall yield from commercially available dichlorodiisopropylsilane. The key step is an asymmetric tandem inter [4 + 2]/intra [3 + 2] cycloaddition between silyoxynitroalkene 17 and chiral vinyl ether (-)-24, illustrating the application of a temporary silicon tether in the tandem nitroalkene cycloaddition process.
A General Strategy for the Synthesis of Cis-Substituted Pyrrolizidine Bases. The Synthesis of (-)-Rosmarinecine
作者:Scott E. Denmark、Atli Thorarensen、Donald S. Middleton
DOI:10.1021/jo00117a002
日期:1995.6
Tandem [4 + 2]/[3 + 2] Cycloadditions of Nitroalkenes. 9. Synthesis of (−)-Rosmarinecine
作者:Scott E. Denmark、Atli Thorarensen、Donald S. Middleton
DOI:10.1021/ja961630x
日期:1996.1.1
general approach for the construction of pyrrolizidines having this stereochemical feature. The key step in the asymmetric synthesis is a Lewisacid-promoted, tandem inter-[4 + 2]/intra-[3 + 2] cycloaddition between a fumaroyloxy nitroalkene and a chiral vinyl ether.