S Reiffers

Rapid synthesis and purification of carbon-11 labelled DOPA: a potential agent for brain studies

A rapid methods for preparation and purification of β-(3,4-dihydroxyphenyl)-D,L-α-alanine-1-11C (11C-DOPA), using 11CO2 as the radioactive precursor is described. Carboxylation of an α-lithioisocyanide, containing protected hydroxylic groups, was followed by a three-step hydrollsis of the intermediate α-isocyano carboxylic acid. Preliminary experiments in rats indicate that the compound is preferentially decarboxylated in brain areas rich in dopamine containing neurons.

Excitation functions for the production of bromine-75: A potential nuclide for the labelling of radiopharmaceuticals

Abstract Based on a theoretical evaluation of the charged particle induced reactions leading to 75 Br the four most promising reactions, 76 Se (p,2n) 75 Br , 76 Se (d,3n) 75 Br , 75 As ( 3 He ,3n) 75 br and 75 As ( 4 He ,4n) 75 Br , were selected for excitation function measurements. From the measured excitation functions the production rates and radionuclide purities were calculated. The proton induced reaction on 76 Se showed the highest production rate (118 mCi/μAh) while the contamination of the undesired nuclide 76 Br is limited to 1.4%.

C-11 LABELED METHYLLITHIUM AS METHYL DONATING AGENT - THE ADDITION TO 17-KETO STEROIDS

Abstract Carbon-11 labelled methyllithium was prepared from 11 C-methyl-iodide by halogen-metal interconversion with n-butyllithium. Within 10 min the exchange was nearly quantitative. The methyl donating properties of this high specific active 11 C-precursor were demonstrated by the addition to 17-keto steroids. 11 C-labelled 17α-methylestradiol, 17α-methyltestosterone and 17α-methylestradiol 3-methylether with specific activities of 1−5 Ci/mmol were prepared.

Preparation of carbon-11 labelled phenylalanine and phenylglycine by a new amino acid synthesis☆

Of the cyclotron-produced short-lived isotopes carbon-11 (t12 = 20.4 min; β+) is one of the most promising as label for radiopharmaceuticals. To prepare 11C-labelled amino acids for evaluation as pancreas scanning agents a new rapid amino acid synthesis was developed. The method is based on the carboxylation of α-lithioisocyanides with 11CO2, followed by hydrolysis of the intermediate reaction product to the desired amino acid. By this method DL-α-phenylalanine-1-11C and DL-α-phenylglycine-1-11C were prepared. The precursor 11CO2 was produced via the 14N(p, α)11C reaction by bombardment of a flow of nitrogen gas mixed with 0.1% O2 with 20 MeV protons. The target system is described.