| abstract |
The present invention provides an improved process for preparation of the L-threo-(2S,3R)-3-(3,4-dihydroxyphenyl)serine (I) or a salt thereof, which is known as Droxidopa; comprising (a) recovery of the by-product compound (V) (as described herein) from the crude compound (I), and (b) recycling and re-use it for the preparation of droxidopa. Accordingly, the present invention relates to an improved economical process for the preparation of L-threo-(2S,3R)-3-(3.4-dihydroxyphenyl)serine (I) or its pharmaceutically acceptable salts; wherein the process relates to recovery and recycling of the by-product compound (V) and also to re-use it for the preparation of droxidopa. |