Preparation of cruciferous phytoalexin related metabolites, (−)-dioxibrassinin and (−)-3-cyanomethyl-3-hydroxyoxindole, and determination of their absolute configurations by vibrational circular dichroism (VCD)
作者:Kenji Monde、Tohru Taniguchi、Nobuaki Miura、Shin-Ichiro Nishimura、Nobuyuki Harada、Rina K Dukor、Laurence A Nafie
DOI:10.1016/s0040-4039(03)01513-2
日期:2003.8
metabolites, (−)-dioxibrassinin (1) and (−)-3-cyanomethyl-3-hydroxyoxindole (2) were prepared from isatin as racemates and were resolved by chiral HPLC. Their absoluteconfigurations were determined by the new chiroptical technique, vibrationalcirculardichroism (VCD), as well as by the conventional electronic circulardichroism (ECD). It is concluded that the absoluteconfigurations of the naturally
Copper-Catalyzed Asymmetric Addition to Isatins to give 3-Hydroxy-2-oxindoles by C-H Activation
作者:Tao Deng、Hongjun Wang、Chun Cai
DOI:10.1002/ejoc.201402852
日期:2014.11
A copper-catalyzedasymmetricaddition to isatins to give3-hydroxy-2-oxindoles by C–Hactivation with a fluorous bis(oxazoline) as ligand is presented. The corresponding products were obtained in 35–66 % yields with enantioselectivities up to 92 %. The fluorous ligand can be easily recovered and reused at least three times without significant loss in its activity.
First asymmetric decarboxylative cyanomethylation of isatins is reported herewith using bifunctional thiourea derived from L-proline in good yields and enantioselectivities. This strategy enables the construction of various 3-cyanomethylene substituted 3-hydroxyoxindoles in enantioselective manner. Enantioselective synthesis of CPC-1 alkaloid has been accomplished in fewer steps.
A direct transition-metal-free asymmetric hydroxylation using commercially available enantiopure Davis oxaziridine as an efficient oxidant is disclosed. An array of medicinally and optically active 3-aryl/alkyl-3-hydroxy-2-oxindoles with a tetrasubstituted stereocenter were obtained in good yields and enantioselectivities. The protocol features ease of operation, scalability, and good functional-group
Asymmetric Rubottom‐Type Oxidation Catalyzed by Chiral Calcium Phosphates
作者:Hualing He、K. S. Satyanarayana Tummalapalli、Linfei Zhu、Minglei Chen、Suvratha Krishnamurthy、Jon C. Antilla
DOI:10.1002/chem.202203720
日期:2023.2.16
A highly efficient catalytic asymmetric Rubottom-type oxidation is described. Using meta-chloroperbenzoic acid (m-CPBA) as the oxidant and chiral calcium phosphate as the catalyst, the facile transformation enables direct hydroxylation of N-Boc oxindoles and β-ketoesters in high yields (up to 99 %) and in a highly enantioenriched fashion (up to >99 % ee).