Method involving 1-benzotriazolyl carbonate esters of poly(ethylene glycol)
The invention provides for preparing a polymer-active agent conjugate, the method comprising the steps of reacting an amino acid derivative with a biologically active agent under conditions to form a polymer-active agent conjugate.
1. A method for preparing a 1-benzotriazolylcarbonate ester of a water-soluble and non-peptidic polymer comprising a protected reactive group, the method comprising:
(i) providing a water-soluble and non-peptidic polymer comprising a protected reactive group and having a structure, R′-POLY-OH, where POLY is a linear polyethylene glycol having a formula, —OCH 2 CH 2 (OCH 2 CH 2 ) n —, R′ is a protected carboxylic acid, and n is an integer selected from about 3 to about 2000, and
(ii) reacting R′-POLY-OH with di(benzotriazolyl)carbonate in an organic solvent in the presence of base to thereby form a 1-benzotriazolylcarbonate ester product having a structure,
where R′ is as described in step (i).
2. The method of claim 1 , wherein the protected carboxylic acid is a protected propionic acid, the protecting group, PG, is selected from benzyl, methyl and ethyl, and the 1-benzotriazolylcarbonate ester product has a structure:
3. The method of claim 2 , wherein PG is benzyl.
4. The method of claim 2 , wherein PG is methyl or ethyl.
5. The method of claim 4 , wherein PG is methyl.
6. The method of claim 4 , wherein PG is ethyl.
7. The method of claim 1 , wherein the organic solvent is selected from the group consisting of methylene chloride, chloroform, acetonitrile, tetrahydrofuran, dimethylformamide, dimethyl sulfoxide, and mixtures thereof.
8. The method of claim 1 , where the base is an amine.
9. The method of claim 8 , wherein the base is selected from the group consisting of pyridine, dimethylaminopyridine, quinoline, trialkylamines, and mixtures thereof.
10. The method of claim 9 , wherein the base is triethylamine.
11. The method of claim 1 , wherein the molar ratio of di(benzotriazolyl)carbonate to R′-POLY-OH in step (ii) is 30:1 or less.
12. The method of claim 3 , where in reacting step (ii), the solvent is acetonitrile and the base is pyridine.
13. The method of claim 12 , wherein reacting step (ii) is carried out at room temperature.
14. The method of claim 13 , wherein the reacting step is carried out under argon.
15. The method of claim 1 , further comprising isolating the 1-benzotriazolylcarbonate ester product from step (ii).
16. The method of claim 12 , wherein the linear polyethylene glycol has a molecular weight of about 2 kilodaltons.