Abstract: An efficient, scaleable synthesis approach towards the spirocyclic oxindole analogue 1'-(tert-butoxycarbonyl)-2-oxospiro [indoline-3, 4'-piperidine]-5-carboxylic acid (1) is described. The key steps are dianion alkylation and cyclization of ethyl 2-oxindoline-5- carboxylate (4) and demethylation of the resulting spirocyclic oxindoleethyl 1'-methyl-2- oxospiro [indoline-3, 4'-piperidine]-5-carboxylate (5). The target compound was obtained ...