Method of preparing carboxylic acid functionalized polymers
Methods for preparing water soluble, non-peptidic polymers carrying carboxyl functional groups, particularly carboxylic acid functionalized poly(ethylene glycol) (PEG) polymers, are disclosed, as are the products of these methods. In general, an ester reagent R(C═O)OR′, where R′ is a tertiary group and R comprises a functional group X, is reacted with a water soluble, non-peptidic polymer POLY-Y, where Y is a functional group which reacts with X to form a covalent bond, to form a tertiary ester of the polymer, which is then treated with a strong base in aqueous solution, to form a carboxylate salt of the polymer. Typically, this carboxylate salt is then treated with an inorganic acid in aqueous solution, to convert the carboxylate salt to a carboxylic acid, thereby forming a carboxylic acid functionalized polymer.
1 . A method for preparing a water soluble, non-peptidic polymer functionalized with a carboxyl group, the method comprising:
i) reacting an ester reagent R(C═O)OR′, where R′ is a tertiary group and R comprises a functional group X, with a water soluble, non-peptidic polymer POLY-Y, where Y is a functional group which reacts with X to form a covalent bond, to form a tertiary ester of the polymer; and
ii) treating the tertiary ester of the polymer with a strong base in aqueous solution, to form a carboxylate salt of the polymer.
2 . The method of claim 1 , further comprising
iii) treating the carboxylate salt of the polymer with an inorganic acid in aqueous solution, to convert the carboxylate salt to a carboxylic acid, thereby forming a carboxylic acid functionalized polymer.
3 . The method of claim 1 , wherein X is a leaving group and Y is a hydroxyl group.
4 . The method of claim 1 , wherein said strong base is an alkali metal hydroxide.
5 . The method of claim 1 , wherein said treating with strong base is effective to produce a reaction pH of about 11 to 13.
6 . The method of claim 2 , wherein said inorganic acid is an acid that produces non-nucleophilic anions in aqueous solution.
7 . The method of claim 6 , wherein the acid is selected from the group consisting of sulfuric acid, nitric acid, phosphoric acid, and hydrochloric acid.
8 . The method of claim 1 , wherein the tertiary ester reagent has the structure:
wherein:
X is a leaving group,
each of R 1 and R 2 is independently selected from hydrogen, alkyl, cycloalkyl, alkoxy, aryl, aralkyl, and heterocycle;
each of R 3 -R 5 is independently selected from lower alkyl, aryl, aralkyl, and cycloalkyl, where any of R 3 -R 5 may be linked to form a ring or ring system;
where any of R 1 to R 5 , excepting hydrogen, may be substituted with a group selected from lower alkyl, lower alkoxy, C 3 -C 6 cycloalkyl, halo, cyano, oxo(keto), nitro, and phenyl; and
n is 1 to about 24.
9 . The method of claim 8 , wherein n is 1 to 6.
10 . The method of claim 9 , wherein n is 1 or 2.
11 . The method of claim 10 , wherein each of R 1 and R 2 is independently hydrogen or unsubstituted lower alkyl, and each of R 3 to R 5 is independently unsubstituted lower alkyl or phenyl.
12 . The method of claim 11 , wherein each of R 1 and R 2 is independently hydrogen or methyl, and each of R 3 to R 5 is independently methyl, ethyl, or phenyl.
13 . The method of claim 12 , wherein each of R 1 and R 2 is H and n is 1.
14 . The method of claim 13 , wherein the tertiary ester reagent is a t-butyl haloacetate.
15 . The method of claim 1 , wherein the polymer is selected from the group consisting of poly(alkylene glycols), poly(olefinic alcohol), poly(vinylpyrrolidone), poly(hydroxyalkylmethacrylamide), poly(hydroxyalkylmethacrylate), poly(saccharides), poly(α-hydroxyacetic acid), poly(acrylic acid), poly(vinyl alcohol), polyphosphazene, polyoxazolines, poly(N-acryloylmorpholine), and copolymers or terpolymers thereof.
16 . The method of claim 15 , wherein the polymer is a poly(ethylene glycol).
17 . The method of claim 16 , wherein the poly(ethylene glycol) is linear and is terminated at one end with said functional group Y and at the other end with another functional group Y′ or a capping group.
18 . The method of claim 2 , further comprising converting the carboxylic acid to an activated carboxylic acid derivative.
19 . The method of claim 18 , wherein said derivative is an activated ester.
20 . The method of claim 18 , further comprising conjugating said polymer with a biologically active molecule, by reacting said carboxylic acid derivative with a functional group on said molecule.
21 . The method of claim 20 , wherein the carboxylic acid derivative is an activated ester, and the functional group on said molecule is a nucleophilic group.
22 . The method of claim 21 , wherein said nucleophilic group is an amino group, a hydroxyl group, or a thiol.
23 . A method for preparing a poly(ethylene glycol) (PEG) functionalized with a carboxyl group, the method comprising:
i) reacting a tertiary ester reagent R(C═O)OR′, where R′ is a tertiary alkyl group and R comprises a functional group X, with a polymer PEG-Y, where Y is a functional group which reacts with X to form a covalent bond, to form a PEG tertiary ester; and
ii) treating the PEG tertiary ester with a strong base in aqueous solution, to form a PEG carboxylate salt.
24 . The method of claim 23 , further comprising
iii) treating the PEG carboxylate salt with an inorganic acid in aqueous solution, to convert the carboxylate salt to a carboxylic acid, thereby forming a PEG carboxylic acid.
25 . The method of claim 23 , wherein X is a leaving group and Y is a hydroxyl group.
26 . The method of claim 23 , wherein said strong base is an alkali metal hydroxide.
27 . The method of claim 24 , wherein the acid is selected from the group consisting of sulfuric acid, nitric acid, phosphoric acid, and hydrochloric acid.
28 . The method of claim 23 , wherein the tertiary ester reagent has the structure:
wherein:
X is a leaving group;
each of R 1 and R 2 is independently selected from hydrogen, alkyl, cycloalkyl, alkoxy, aryl, aralkyl, and heterocycle;
each of R 3 -R 5 is independently selected from lower alkyl, aryl, aralkyl, and cycloalkyl, where any of R 3 -R 5 may be linked to form a ring or ring system;
where any of R 1 to R 5 , excepting hydrogen, may be substituted with a group selected from lower alkyl, lower alkoxy, C3-C6 cycloalkyl, halo, cyano, oxo(keto), nitro, and phenyl; and
n is 1 to about 24.
29 . The method of claim 28 , wherein n is 1 to 6.
30 . The method of claim 29 , wherein n is 1 or 2.
31 . The method of claim 28 , wherein each of R 1 and R 2 is independently hydrogen or unsubstituted lower alkyl, and each of R 3 to R 5 is independently unsubstituted lower alkyl or phenyl.
32 . The method of claim 28 , wherein each of R 1 and R 2 is H and n is 1.
33 . The method of claim 32 , wherein the tertiary ester reagent is a t-butyl haloacetate.
34 . The method of claim 23 , wherein the poly(ethylene glycol) is linear and is terminated at one end with said functional group Y and at the other end with another functional group Y′ or a capping group.
35 . The method of claim 23 , wherein the PEG has a molecular weight of about 100 to about 100,000 Da.
36 . The method of claim 35 , wherein the PEG has a molecular weight of about 300 to about 60,000 Da.
37 . The method of claim 24 , further comprising converting the PEG-carboxylic acid to an activated carboxylic acid derivative.
38 . The method of claim 37 , wherein said derivative is an activated ester.
39 . The method of claim 37 , further comprising conjugating said PEG with a biologically active molecule, by reacting said carboxylic acid derivative with a functional group on said molecule.
40 . An isolated polymer product comprising a carboxylic acid functionalized polymer, made by the method of claim 2 ,
wherein the product contains less than 5% by weight of said POLY-Y polymer, with the balance consisting essentially of said carboxylic acid functionalized polymer.
41 . The polymer product of claim 40 , containing less than 2% by weight of said POLY-Y polymer.
42 . The polymer product of claim 40 , containing less than 0.5% by weight of said POLY-Y polymer.
43 . The polymer product of claim 40 , containing substantially no amount of low molecular weight organic acid.
44 . The polymer product of claim 40 , containing substantially no amount of monomeric organic carboxylic acid.
45 . The polymer product of claim 40 , containing substantially no amount of trifluoroacetic acid.
46 . The polymer product of claim 40 , wherein said carboxylic acid functionalized polymer is a PEG carboxylic acid.
47 . The polymer product of claim 46 , wherein said carboxylic acid functionalized polymer is mPEG-CH 2 —COOH, and said polymer product contains less than 5% by weight of mPEG-OH.
48 . The polymer product of claim 47 , containing less than 2% by weight of mPEG-OH.
49 . The polymer product of claim 48 , containing less than 0.5% by weight of mPEG-OH.
50 . The polymer product of claim 49 , containing substantially no amount of trifluoroacetic acid.
51 . The polymer product of claim 46 , wherein said carboxylic acid functionalized polymer is HOOC—CH 2 —PEG-CH 2 —COOH, and said product contains less than 5% by weight of HO-PEG-OH.
52 . The polymer product of claim 51 , containing less than 0.5% by weight of HO-PEG-OH.
53 . The polymer product of claim 52 , containing substantially no amount of trifluoroacetic acid.
54 . The polymer product of claim 46 , wherein said carboxylic acid functionalized polymer is a multifunctional branched or multiarm carboxylic acid functionalized PEG represented by PEG-(CH 2 —COOH) x , where x is 3 to 8, and said product contains less than 5% by weight of PEG-(OH) x .
55 . The polymer product of claim 54 , containing substantially no amount of trifluoroacetic acid.
56 . In a method of preparing a poly(ethylene glycol) (PEG)polymer functionalized with a carboxyl group, by reaction of a tertiary ester reagent R(C═O)OR′, where R′ is a tertiary alkyl group and R comprises a functional group X, with a polymer PEG-Y, where Y is a functional group which reacts with X to form a covalent bond, to form a PEG tertiary ester,
an improvement comprising:
treating the PEG tertiary ester with a strong base in aqueous solution, to form a PEG carboxylate salt.
57 . The improvement of claim 56 , wherein the method further comprises
treating the PEG carboxylate salt with an inorganic acid in aqueous solution, to convert the carboxylate salt to a carboxylic acid, thereby forming a PEG carboxylic acid.
58 . The improvement of claim 56 , wherein said strong base is an alkali metal hydroxide.
59 . The improvement of claim 56 , wherein said treating with strong base is effective to produce a reaction pH of about 11 to 13.
60 . The improvement of claim 57 , wherein the acid is selected from the group consisting of sulfuric acid, nitric acid, phosphoric acid, and hydrochloric acid.