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Aspects of 6-[18F]fluoro-L-DOPA Preparation. Deuterochloroform as a Substitute Solvent for Freon 11

Aspects of 6-[18F]fluoro-L-DOPA Preparation. Deuterochloroform as a Substitute Solvent for Freon 11

F Füchtner, J Zessin, P Mäding, F Wüst

Nuklearmedizin. 2008;47(1):62-4.

PMID: 18278215

Abstract:

Aim:
Replacement of the ecologically harmful solvent Freon 11 (CFCl(3)) by chloroform for the module-assisted preparation of 6-[(18)F]fluoro-L-DOPA based on the electrophilic radiofluorodestannylation of the precursor N-formyl-3,4-di-tert-butoxycarbonyloxy-6-(trimethylstannyl)-L-phenylalanine ethyl ester.
Materials, methods:
The TRACERlab Fx FDOPA module (GE Medical Systems) was used for the preparation of 6-[(18)F]fluoro-L-DOPA. Cyclotron-produced [(18)F]F(2) gas (5 GBq) was passed through a cooled solution (5 degrees C) of the stannyl precursor (45 mg) in CDCl(3) (10 ml). After the [(18)F]fluorination step, HCl (2 ml, 6 mol/l) was added to the solution. Then the reaction mixture was heated at 80 degrees C for 5 min under vacuum to evaporate the chloroform. The hydrolysis to remove the protecting groups was completed by heating the closed reactor at 130 degrees C for 8 min. After cooling to 20 degrees C the reaction mixture was purified by HPLC with two polymer-based RP columns (PRP-1, 7 microm, 10 x 250 mm, Hamilton) using a solution of AcOH/AcONa (pH 4.7) as eluent. The 6-[(18)F]fluoro-L-DOPA fraction was collected and sterile filtrated.
Results:
Three types of stabilised chloroform were tested for the radiofluorination of the precursor. Only by use of deuterochloroform stabilised with silver no significant losses of radioactivity were observed. Thus, 6-[(18)F]fluoro-L-DOPA purified by HPLC was obtained in decay-corrected radiochemical yields of 25+/-3%, ready for human use.
Conclusion:
CDCl(3) has proved to be a convenient solvent for the module-assisted preparation of 6-[(18)F]fluoro-L-DOPA. In this way the use of the polluting Freon 11 can be avoided.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AP37178373	L-Dopa ethyl ester		37178-37-3	Price

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