	US 7,608,663 B2
	Method of preparing propionic acid-terminated polymers
Antoni Kozlowski, Huntsville, Ala. (US); and Samuel P. McManus, Huntsville, Ala. (US)
Assigned to Nektar Therapeutics, San Carlos, Calif. (US)
Filed on Jan. 21, 2005, as Appl. No. 11/40,142.
Claims priority of provisional application 60/538006, filed on Jan. 21, 2004.
Prior Publication US 2005/0171291 A1, Aug. 04, 2005
Int. Cl. C08G 65/08 (2006.01); C08G 65/332 (2006.01); C08F 8/12 (2006.01); C08F 8/14 (2006.01)

U.S. Cl. 525—59 [525/61; 525/259; 525/307; 525/326.1; 525/328.8; 525/329.7; 525/330.3; 525/404; 525/408; 525/409; 525/523; 525/530; 525/531]

28 Claims

1. A method for preparing a water soluble and non-peptidic polymer functionalized with at least one propionic acid group, the method comprising:

i) reacting a water soluble and non-peptidic polymer comprising at least one hydroxyl group with a tertiary alkyl acrylate in the presence of a catalyst comprising a quaternary ammonium salt to form a propionic acid ester of the polymer, wherein the polymer has a weight average molecular weight of at least about 10,000 Da; and

ii) treating the propionic acid ester of the polymer with a strong acid to form a propionic acid-functionalized polymer;

with the proviso that the water soluble and non-peptidic polymer functionalized with at least one propionic acid group is neither methoxy PEG propionic acid having a weight average molecular weight of about 20,000 Da, nor methoxy PEG propionic acid having a weight average molecular weight of about 30,000 Da.