Total Synthesis Of Indole-3-Acetonitrile-4-Methoxy-2-C-?-D-Glucopyranoside. Proposal For Structural Revision Of The Natural Product
Indole-3-acetonitrile-4-methoxy-2-C-?-D-glucopyranoside (1), a novel C-glycoside from Isatis indigotica with important cytotoxic activity, has been prepared in ten steps from ethynyl-?-C-glycoside 3 and 2-iodo-3-nitrophenyl acetate 6. Key steps in the synthesis include a Sonogashira coupling and a CuI-mediated indole formation. NMR spectrocopic data for synthetic 1 differs from that reported for the natural product. A revised structure for the natural product, containing an alternate carbohydrate substituent, is proposed.