x-methyl ester Prep Kit

Amount: 100mg

Item Name: Amino-dPEG®12-methyl ester Prep KIT

Item #: 10334

Mol. Wt.: 631.75;

single compound dPEG®Spacer is 40 atoms and 46.5 A

Product Features and Benefits: Note: The amino-dPEG®methyl esters are not stable upon prolonged storage. Therefore we could not store them for you, our customers. So we have developed kits in order to make these valuable pegylation compounds available in a pure form in situ Kit contains three component parts: a) 1 eq. of amino-dPEG® acid; b) 1.5 eq. of p-toluene sulfonic acid; c) sufficient dry methanol for the package size. Methyl protected dPEG®amino acid: dPEG®pegylation spacer and modifier containing a reactive amine. Methyl group is removed with mild base once the amine is reacted. dPEG®pegylation spacer is hydrophilic, highly water soluble and non-immunogenic. The ester is water soluble, as well as being soluble in a variety of organic solvents especially methylene chloride. Contrasting the t-butyl group, the methyl group can be easily removed with base, either KOH or with a carbonate base, e.g., potassium carbonate in aqueous methanol. This can be done in an aqueous or combination aqueous organic solvent system. The specific conditions are going to be dictated by the stability of the system into which the methyl ester is being introduces. Methyl group can also, like the t-Butyl group provide a potential purification handle due to its hydrophobicity. Subsequently it is removed to perform additional chemistry. This applies best when using normal phase (e.g., silica gel) chromatography. The methyl group neutralizes the zwitterion of the amino acid for better reactivity at the amine Protocol : a) Preperation of the methyl ester in situ: In a dry flask, add the 100 mg of p-toluenesulfonic acid (PN 10002) and place in an ice bath. While keeping the contents under a dry atmosphere (e.g. with a drying tube or with nitrogen) slowly add 1 ml of dry methanol (PN 10003) with stirring, and then stir for 5 minutes at this temperature. Subsequently, add the 100 mg of the amino-dPEG®acid in one portion to this solution and allow the mixture to stir at ambient temperature until the reaction is complete by TLC.1 This will typically take about 3-4 hours. To use the amino-dPEG®4 methyl ester, you can proceed with the methanol solution, if this solvent is compatible, or remove the solvent and replace it with one that is, the choice can include water. At this stage the product is stable if stored at +4oC or lower for short periods of time (days). When using the product, you will need to compensate for the 1.5 equivalents of p-toluenesulfonic acid in the product with the supplemental addition of 1.5 equiv. of base. When reacting in an organic solvent we most often use triethylamine, diisopropylethylamine or 2,6-lutidine, e.g., when reacting with active esters. IN AQUEOUS, care must be taken NOT to hydrolyze the methyl ester at elevated pH’s (>7). 1TLC data: The solvent is typically something like methanol: methylene chloride: ethyl acetate: ammonium hydroxide, 1:2:2:0.2 or 1 ml: 2 ml: 2 ml: 10 drops, run on a silica gel normal phase plate and developed with a ninhydrin spray. E.g. the Rf of the amino-dPEG®4 methyl ester is about 0.4. And when the reaction is complete, it will be one clean spot on the plate. 2 Important Note: We had previously offered the amino-dPEG®methyl esters as an individual products, but have found that upon extended storage the material polymerizes (amine reaction with the methyl ester). b) Reaction with active ester: Find a solvent in which active ester is soluble (methylene chloride is a preferred solvent) and dissolve the ester in the dry solvent, add triethylamine, then add the amine, either neat or drop wise as a solution in the reaction solvent. Use at least a 10% excess of all reagents relative to the active ester. This can be carried out at ambient temperatures. c) a free acid: generate the active ester in situ with EDC and NHS or HOBt, then add the triethylamine, followed by the amino-dPEG®4 t-butyl ester; or ii) combine the acid, NHS or HOBt, TEA, and the amino-dPEG®methyl ester, and add a solution of the EDC. Use at least a 10% excess of reagents relative to...