Total synthesis of indole-3-acetonitrile-4-methoxy-2-C-β-d-glucopyranoside. Proposal for structural revision of the natural product

Abstract

Indole-3-acetonitrile-4-methoxy-2-C-β-D-glucopyranoside (1), a novel C-glycoside from Isatis indigotica with important cytotoxic activity, has been prepared in ten steps from ethynyl-β-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 spectroscopic 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.