Barium carbonate building blocks

Barium Carbonate and the Preparation of Carbon-14-Labeled Compounds via One-Carbon Building Blocks of the... 

Acetylene, which can be prepared in high yield from barium [ C]carbonate, is most often used for the production of [U- C]benzene, and thence avast array of labeled aromatic compounds. The preparation and handling of [ C2]acetylene is not difficult to achieve in the average radiochemistry laboratory, and it has been used as a two-carbon building block in a variety of syntheses. In addition, it is the source of a number of other two- to four-carbon building blocks, making its utility relatively broad, even aside from its uses as the source of [U- C]aromatic derivatives. 

Synthetic chemical approaches to the preparation of carbon-14 labeled materials iavolve a number of basic building blocks prepared from barium [ CJ-carbonate (2). These are carbon [ C]-dioxide [ CJ-acetjlene [U— C]-ben2ene, where U = uniformly labeled [1- and 2- C]-sodium acetate, [ C]-methyl iodide, [ C]-methanol, sodium [ C]-cyanide, and [ CJ-urea. Many compHcated radiotracers are synthesized from these materials. Some examples are [l- C]-8,ll,14-eicosatrienoic acid [3435-80-1] inoxn. [ CJ-carbon dioxide, [ting-U— C]-phenyhsothiocyanate [77590-93-3] ftom [ " CJ-acetjlene, [7- " C]-norepinephrine [18155-53-8] from [l- " C]-acetic acid, [4- " C]-cholesterol [1976-77-8] from [ " CJ-methyl iodide, [l- " C]-glucose [4005-41-8] from sodium [ " C]-cyanide, and [2- " C]-uracil [626-07-3] [27017-27-2] from [ " C]-urea. All syntheses of the basic radioactive building blocks have been described (4). 

Figure 5.1 Barium fCJcarbonate and the first generation of one- and two-carbon f" C] building blocks...

Chapter 5 introduces carbon-14 the isotope, barium [ C]carbonate the main form for storage and commerce, and [ C]carbon dioxide as a building block in radiochemical synthesis. The chapter also describes the conversion of into one-[ C]carbon... 

Its barium salt is the source of a number of additional carbon-14 buUding blocks, such as [ CJguanidine, [ CJurea and [ C]thiourea. [ C]Cyanamide is itself also a versatile building block. The utility of each of these for the synthesis of carbon- 14-labeled compounds is discussed in the Sections below. 

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