The present invention relates to a novel and industrially advantageous process for the preparation of 5-substsituted indole derivative, particularly it relates to process for the preparation of 5-bromo-3-[(R)-l-methyl-pyrrolidin-2-ylmethyl]-lH-indol of formula I, a key intermediate for the synthesis of eletriptan or pharmaceutically acceptable salts thereof, through novel keto carbamate intermediate of formula, wherein R is selected from hydrogen, alkyl, alkoxy, aryloxy, nitrile, nitro, halo
