Nucleophilic radioiodination of 6-bromocholesterol via non-isotopic exchange reaction in molten state

M. El-Tawoosy

doi:10.1023/a:1013229827935

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Journal of Radioanalytical and Nuclear Chemistry

Volume/Issue:: Volume 249: Issue 3

Nucleophilic radioiodination of 6-bromocholesterol via non-isotopic exchange reaction in molten state

Author:

M. El-Tawoosy

M. El-Tawoosy Atomic Energy Authority Labelled Compounds Department, Radioisotope Production Division, Hot Labs. Centre P.O. Box 13759 Cairo Egypt

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Pages:: 535–540

Online Publication Date:: 29 Oct 2004

Publication Date:: 17 Sep 2001

Article Category:: Research Article

DOI:: https://doi.org/10.1023/a:1013229827935

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Abstract

A synthetic method for preparing radioiodinated 6-[125 I]iodocholesterol[CL-6-125 I] for adrenal evaluation is described. The radioiodine atom wasincorporated onto the cholesterol molecule via non-isotopic exchange between6-bromocholesterol [CL-6-Br] and radioiodine as iodide ion [ 125 I –]in a molten state. The different parameters affecting the yield of exchange were investigated using 125 I (T 1/2 .60 d) to centralize the different physical and chemical reaction conditions and purification of the final product as pure as 6-[125 I]iodocholesterol. The method was suitable to either 131 I (T 1/2 .8 d) nucleophilic radioiodination which facilitates the scanning of the adrenal for a few days after administration or the use of 124 I (T 1/2 .4.16 d) nucleophilic radioiodination for PET evaluation of the adrenal. TLC as well as HPLC chromatographic analysis is used to determine the efficiency of the exchange reactions under different chemical reaction conditions and to monitor the stability of the final product as pure as CL-6-125 I with radiochemical purity of .99%. This no-carrier-added method improved the speed of the reaction and affords high radiochemical yield of 90 % and suitable specific activity due to the use of CL-6-Br rather than CL-6-I as substrate. Kinetic studies revealed second order iodine-bromine exchange reaction. The activation energy for the exchange reaction in ammonium acetate (m.p. 114 °C) was calculated to be 4.576 kcal/mole.

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Journal of Radioanalytical and Nuclear Chemistry

Print ISSN:: 0236-5731

Online ISSN:: 1588-2780

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Journal of Radionalytical and Nuclear Chemistry
Language	English
Size	A4
Year of Foundation	1968
Volumes per Year	1
Issues per Year	12
Founder	Akadémiai Kiadó
Founder's Address	H-1117 Budapest, Hungary 1516 Budapest, PO Box 245.
Publisher	Akadémiai Kiadó Springer Nature Switzerland AG
Publisher's Address	H-1117 Budapest, Hungary 1516 Budapest, PO Box 245. CH-6330 Cham, Switzerland Gewerbestrasse 11.
Responsible Publisher	Chief Executive Officer, Akadémiai Kiadó
ISSN	0236-5731 (Print)
ISSN	1588-2780 (Online)