1. A process of the preparation of Tiopronin (1)
comprising:
a) Chlorinating 2-chloropropionic acid (6)
with a suitable chlorinating agent to form 2-chloropropanoyl chloride (5);
b) coupling glycine (4)
with intermediate (5) in presence of a suitable base to form 2-(2-chloropropanamido) acetic acid (3);
c) reacting intermediate (3) with potassium thioacetate to form 2-(2-(acetylthio) propanamido) acetic acid (2);
15

and d) hydrolyzing intermediate (2) using a suitable base to form Tiopronin
(1)-
2. The process, as claimed in claim 1, wherein the suitable chlorinating agent
is selected from a group comprising of chlorine, hydrochloric acid gas, thionyl chloride, oxalyl chloride, phosphorus trichloride, phosphoryl chloride, phosphorus pentachloride, methane sulfonyl chloride, trichloromethanesulfonyl chloride, tert-butyl hypochlorite, methoxyacetyl chloride, n-chlorosuccinimide, n-chlorophthalimide, sodium dichloroisocyanurat, trichloroisocyanuric acid or mixtures thereof.
3. The process, as claimed in claim 1, wherein the suitable base used in step b) and step d) is selected from sodium bicarbonate, potassium bicarbonate, lithium bicarbonate, cesium bicarbonate, sodium methoxide, sodium ethoxide; potassium methoxide, potassium ethoxide, sodium butoxide, potassium butoxide, potassium-t-butoxide, sodium tertiary butoxide, lithium methoxide, sodium hydroxide, potassium hydroxide, lithium hydroxide, lithium hydroxide, monohydrate Preferably, sodium bicarbonate and lithium hydroxide monohydrate were used in the present invention
4. A process for the purification of Tiopronin (1) comprising:

a) adding Tiopronin (1) in a suitable aprotic solvent or mixture thereof;
b) heating the reaction mixture to a suitable temperature;
c) cooling the reaction mixture; and
d) isolating pure Tiopronin (1).

5. The process, as claimed in claim 4, wherein the Tiopronin (1) obtained after purification is having purity greater than 99.0% (w/w).
6. The process, as claimed in claim 4, wherein the Tiopronin (1) was having impurities A, B, C, D and E less than 1.0% (w/w).
7. The process, as claimed in claim 4, wherein the crystalline Tiopronin (1) is having XRD as illustrated in figurel and with 20 (theta) ± 0.2 values of 10.13, 11.21, 12.51, 13.84, 16.29, 17.09, 19.14, 19.93, 21.20, 22.41, 23.86, 25.52, 25.88, 26.49, 27.76, 29.55, 31.40, 34.78, 36.17, 37.67, 38.42 and 38.92.