T T V V1U1111 ■
1. A process for the preparation of Gadoteridol of formula (la) having purity greater than 99.5%
comprising:
a. reacting 1,4,7,10-tetraazacyclododecane of formula (6)
w
with tert-butyl 2-bromoacetate of formula (5)
. 1 ~
to obtain tert-butyl 2,2',2"-(l,4,7,10-tetraazacyclododecane-l,4,7-triyl) triacetate hydrobromide of formula (4);
b. hydrolyzing tert-butyl 2,2',2"-(l,4,7,10-tetraazacyclo dodecane-1,4,7-triyl) triacetate hydrobromide of formula (4) to 2,2',2"-(1,4,7,10-tetraazacyclododecane-l,4,7-triyl) triacetic acid of formula (3), optionally isolating intermediate of formula (3);

c. alkylating 2,2',2"-(l,4,7,10-tetraazacyclododecane-l,4,7-triyl)
triacetic acid compound of formula (3) with propylene oxide of formula (2)
v-/
and treating with a suitable acidic resin to yield 2,2',2"-(10-(2-
hydroxypropyl)-l ,4,7,10-tetraazacyclo dodecane-1,4,7-triyl)
triacetic acid of formula (1); and
d. complexing 2,2',2"-(10-(2-hydroxypropyl)-l,4,7,10
tetraazacyclododecane-l,4,7-triyl) triacetic acid of formula (1) with Gadolinium oxide to yield Gadoteridol of formula (la). Optionally purifying formula (la), which comprises of;
a) providing a solution of Gadoteridol of formula (la) in protic solvent or mixture of solvents thereof;
b) adjusting the pH of the solution to 3.0-4.0 by adding suitable acidic resin;
c) optionally, filtering the reaction mass;
d) adjusting the pH of the solution to 7.0-8.0 by adding suitable basic resin; and
e) isolating pure Gadoteridol of formula (la).

2. The process as claimed in claim 1, wherein the suitable resin used in the present invention is selected from the group comprising of 225 H+ Acidic resin, Indion 225 Na, Indion 220 Na, Indion 225 H, Indion 225 H (MB), Indion 236, Indion 740, Indion 730, Amberlite IRC 50, Indion 810 "OH basic resin or Amberlite IRA 67.
3. The process as claimed in claim 1, wherein the Gadoteridol of formula (la) having purity greater than 99.5% and characterized by one or more of the following:
a. less than 5ppm of Iron content;
b. less than 10 ppm of free Gadolinium content; and
c. less than 0.01% (w/w) of impurity A.
4. The process as claimed in claim 1, wherein Gadoteridol of formula (la) is having regio isomer of formula (13) content less than 1.0% (w/w).
5. A process for the purification of Gadoteridol of formula (la) comprising;
a. providing a solution of Gadoteridol of formula (la) in protic
solvent or mixture of solvents thereof;

b. adjusting the pH of the solution to 3.0 to 4.0 using suitable acidic
resin;
c. optionally, filtering the reaction mass;
d. adjusting the pH of the solution to 7.0-8.0 by adding suitable
basic resin; and
e. isolating pure Gadoteridol of formula (la).
6. The process as claimed in claim 5, wherein the suitable protic solvent is selected from the group comprising of methanol, ethanol, isopropanol, propanol, butanol, water or mixtures thereof.
7. A process for the preparation of high purity Calteridol calcium of formula (lb) is having purity greater than 99.0%
comprising:
a. reacting 1,4,7,10-tetraazacyclododecane of formula (6)
with tert-butyl 2-bromoacetate of formula (5)
(5)
to obtain tert-butyl 2,2',2"-(l,4,7,10-tetraazacyclododecane-l,4,7-triyl) triacetate hydrobromide of formula (4);

b. hydrolyzing tert-butyl 2,2',2"-(l,4,7,10-tetraazacyclo dodecane-1,4,7-triyl) triacetate hydrobromide of formula (4) to 2,2',2"-(l,4,7,10-tetraazacyclododecane-l,4,7-triyl) triacetic acid of formula (3), optionally isolating intermediate of formula (3);
c. alkylating 2,2',2"-(l,4,7,10-tetraazacyclododecane-l,4,7-triyl)
triacetic acid compound of formula (3) with propylene oxide of formula (2)
and reacting with a suitable acidic resin furnished chelating ligand 2,2',2"-(l 0-(2-hydroxypropyl)-1,4,7,10-tetraazacyclo dodecane-1,4,7-triyl) triacetic acid of formula (1) ; and
d. complexing 2,2',2"-(10-(2-hydroxypropyl)-1,4,7,10
tetraazacyclododecane-l,4,7-triyl) triacetic acid of formula (1) with calcium ion source to yield Calteridol calcium of formula (lb).

8. A process for the preparation of Calteridol calcium of formula (lb)
comprising:
a. de-complexing the gadoteridol of formula (la) with suitable de-
complexing agent to obtain 2,2',2"-(10-(2-hydroxypropyl)-l,4,7,10-
tetraazacyclododecane-l,4,7-triyl) triacetic acid of formula (1); and
b. complexing the formula (1) with a calcium ion source to yield
Calteridol calcium of formula (lb).
9. The process as claimed in claim 8, wherein the calcium source is selected
from a group comprising of calcium hydroxide, calcium oxide, calcium
carbonate calcium chloride or calcium acetate.
10. The process as claimed in claim 7, wherein Calteridol calcium of formula (lb) is having regio isomer of formula (13) content less than 1.0% (w/w).
11. The process as claimed in claim 7, wherein compound of formula (1) is purified by the process comprising;
a. providing a solution of formula (1) in a suitable protic solvent or
mixture of solvents thereof;
b. treating the reaction mixture with acidic and basic resin;
c. optionally, treating with activated carbon; and
d. isolating pure compound of formula (1).