Catalytic Asymmetric Synthesis of Substituted 3-Hydroxy-2-Oxindoles
作者:Nadine V. Hanhan、Aziza H. Sahin、Toby W. Chang、James C. Fettinger、Annaliese K. Franz
DOI:10.1002/anie.200904393
日期:2010.1.18
used to catalyze the addition of indoles and other π nucleophiles to N‐alkylated and unprotected isatins (see picture). The resulting biologically relevant substituted3‐hydroxy‐2‐oxindoles were obtained in high yield with high enantioselectivity. Tf=trifluoromethanesulfonyl.
Catalytic Asymmetric [3+2] Annulation of Allylsilanes with Isatins: Synthesis of Spirooxindoles
作者:Nadine V. Hanhan、Nicolas R. Ball-Jones、Ngon T. Tran、Annaliese K. Franz
DOI:10.1002/anie.201105739
日期:2012.1.23
Silyl‐inspired spirocycle: The title reaction is the first example of a catalytic asymmetric [3+2] annulation reaction with allylsilanes. The annulation reaction utilizes a chiral ScCl2(SbF6)/L catalyst and TMSCl as a promoter to afford spirooxindoles in excellent enantioselectivity at room temperature. The SiC bond can be oxidized to deliver hydroxy‐substituted spirooxindoles. TMS=trimethylsilyl
Scandium(III)-Catalyzed Enantioselective Allylation of Isatins Using Allylsilanes
作者:Nadine V. Hanhan、Yng C. Tang、Ngon T. Tran、Annaliese K. Franz
DOI:10.1021/ol300496v
日期:2012.5.4
The scandium(III)-catalyzed enantioselective Hosomi-Sakurai allylation of isatins with various substituted allylic silanes is described. A catalyst loading as low as 0.05 mol % Is utilized at room temperature to afford the 3-allyl-3-hydroxy-2-oxindoles in excellent yields and enantioselectivity up to 99% ee, including a demonstration of a gram-scale reaction. The effects of additives and varying silyl groups were explored to demonstrate the scope and application.
6-Bromoindole Derivatives from the Icelandic Marine Sponge Geodia barretti: Isolation and Anti-Inflammatory Activity
An UPLC-qTOF-MS-based dereplication study led to the targeted isolation of seven bromoindole alkaloids from the sub-Arctic sponge Geodia barretti. This includes three new metabolites, namely geobarrettin A⁻C (1⁻3) and four known compounds, barettin (4), 8,9-dihydrobarettin (5), 6-bromoconicamin (6), and l-6-bromohypaphorine (7). The chemical structures of compounds 1⁻7 were elucidated by extensive