Itsenko Oleksiy, Långström Bengt
Department of Organic Chemistry, Institute of Chemistry, Uppsala University, Box 531, S-751 21 Uppsala, Sweden.
J Org Chem. 2005 Mar 18;70(6):2244-9. doi: 10.1021/jo047806s.
[reaction: see text] [carboxyl-(11)C]Carboxylic acids were prepared from alkyl iodides via photoinitiated radical reactions using 10(-)(8) mol of [(11)C]carbon monoxide in binary and ternary homogeneous solvent mixtures. Short- (isobutyric), medium-, and long-chain saturated fatty acids (heptadecanoic) were labeled with isolated decay-corrected radiochemical yields ranging from 55% to 70% in 5-7-min reactions. The conversion of [(11)C]carbon monoxide to products reached 80-90%. To obtain good yields in the reactions performed in water-acetonitrile and water-THF mixtures, the addition of tetrabutylammonium hydroxide or potassium hydroxide was essential. The carboxylation was efficient for primary and secondary alkyl iodides. The carboxylation of tertiary iodides was feasible for 1-iodoadamantane but not for tert-butyl iodide. The dependence of the radiochemical yields on reaction time, photoirradiation conditions, and organic and inorganic additives was studied. The method provides a one-step route to [carboxyl-(11)C]carboxylic acids; traditional methods, in contrast, would require several steps. For example, using the devised reaction conditions, 3.19 GBq of purified [1-(11)C]1,10-decanedicarboxylic acid (specific radioactivity 188 GBq/mumol) was obtained within 35 min of the end of 10 muAh bombardment. (1-(13)C)4-Phenylbutyric acid was synthesized using ((13)C)carbon monoxide for identifying the labeling position with (1)H and (13)C NMR.
[反应：见正文] 通过光引发自由基反应，使用10⁻⁸摩尔的[(¹¹)C]一氧化碳，在二元和三元均相溶剂混合物中由烷基碘制备了[羧基-(¹¹)C]羧酸。短链（异丁酸）、中链和长链饱和脂肪酸（十七烷酸）在5至7分钟的反应中被标记，经分离衰变校正后的放射化学产率为55%至70%。[(¹¹)C]一氧化碳转化为产物的转化率达到80%至90%。为了在水-乙腈和水-四氢呋喃混合物中进行的反应中获得良好产率，添加氢氧化四丁基铵或氢氧化钾至关重要。羧化反应对伯烷基碘和仲烷基碘有效。叔碘化物的羧化反应对于1-碘代金刚烷是可行的，但对于叔丁基碘则不可行。研究了放射化学产率对反应时间、光辐照条件以及有机和无机添加剂的依赖性。该方法提供了一条制备[羧基-(¹¹)C]羧酸的一步路线；相比之下，传统方法需要多个步骤。例如，使用设计的反应条件，在10 μAh轰击结束后的35分钟内获得了3.19 GBq的纯化[1-(¹¹)C]1,10-癸二酸（比活度188 GBq/μmol）。使用[(¹³)C]一氧化碳合成了(1-(¹³)C)4-苯基丁酸，用于通过¹H和¹³C NMR确定标记位置。
