Diastereospecific synthesis of ketooxindoles. Potential intermediates for the synthesis of alstonisine as well as for voachalotine related oxindole alkaloids

Article abstract of DOI:10.1016/S0040-4039(97)10420-8

A convenient method has been developed to convert N(a)-H tetracyclicketone la into the two corresponding oxindolesr[(7)] diastereospecifically. Treatment of the N(a)-H, N(b)-benzyl tetracyclicketone 1a with t-BuOCl provided diastereomer 2a (related to Voacanga oxindoles), whereas the same process with Nb-H (1b) or N(b)-benzoyl (1c) substituted analogs funished the diastereomers 2b and 2c (related to alstonisine), respectively.