The present invention provides an improved process for preparing (S)-4-[3-[2-(dimethylamino)ethyl]-1H-indol-5-yl]methyl}-2-oxazolidinone which comprises: a) forming a carbamate of formula (III), from methyl 4-nitro-(L)-phenylalaninate hydrochloride; b) reducing the compound of formula (III) to give the compound of formula (IV); c) reducing the methyl ester grouping in the compound of formula (IV) to give the compound of formula (V); d) ring closure of the compound of formula (V) to give the compound of formula (VI); e) diazonium salt formation from the compound of formula (VI) followed by reduction to give the compound of formula (VII); f) Fischer reaction of the compound of formula (VII) to give (S)-4-[3-[2-(dimethylamino)ethyl]-1H-indol-5-yl]methyl}-2-oxazolidinone.