The invention provides a method for preparing a 1 benzotriazolylcarbonate ester of a water soluble and non peptidic polymer by reacting a terminal hydroxyl group of a water soluble and non peptidic polymer with dicarbonate in {HEAD ~ the presence} of an amine base and {TAIL ~ an organic solvent} 
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The invention provides a method for preparing a 1 benzotriazolylcarbonate ester of a water soluble and non peptidic polymer by reacting a terminal hydroxyl group of a water soluble and non peptidic polymer with dicarbonate in { HEAD ~ the presence } of an amine base and { TAIL ~ an organic solvent }
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