ABSTRACT
This report describes a highly efficient ß-selective C-glycosylation of bicyclic galactals with 2-oxindoles through a palladium-catalyzed decarboxylative pathway. A variety of substrates representing both glycosyl donors and acceptors could be transformed in greater than 90% yields under mild reaction conditions. The decarboxylation intermediate of galactal could serve as an efficient base to deprotonate the enol tautomer of 2-oxindole and enhance its nucleophilicity. The ß-selective nucleophilic addition at the anomeric center originates from the steric hindrance imposed by the palladium and bulky ligand.
Subject(s)
Oxindoles , Palladium , Catalysis , Galactose/analogs & derivatives , Galactose/chemistry , Glycosylation , Ligands , Oxindoles/chemistry , Palladium/chemistryABSTRACT
Mohangic acids are a class of p-aminoacetophenonic acids that contain a conjugated triene or diene moiety. Herein, this paper reports two new mohangic acids E and F (1-2) together with a known compound mohangic acid A (3), which were isolated from the deep-sea sediment-derived bacteria Alcanivorax dieselolei BC-5. The structures of 1 and 2 were established by HRESIMS, 1 D and 2 D NMR, and IR spectroscopy.
ABSTRACT
Two new alkaloids (1,2) and one new enoic acid (3), together with three known piericidins (4-6), were isolated from the liquid fermentation of the salt lake derived Streptomyces sp. QHA10. The structures of 1-3 were elucidated based on extensive spectroscopic data (NMR, HRESIMS) as well as single-crystal X-ray diffraction. Compound 3 showed potential anti-inflammatory activity by inhibiting the production of nitric oxide (NO) in lipopolysaccharide (LPS)-induced RAW 264.7 mouse macrophages with the IC50 value of 24.5 µM.
