会議発表用資料 A preliminary study of facile [11C]cyanide preparation from [11C]methyl iodide

Kikuchi, Tatsuya  ,  Ming-Rong, Zhang  ,  D. Gee, Antony

2017-05-16
内容記述
Introduction. [11C]Cyanide has been used as a useful intermediate for incorporation of 11C-labelled functional groups such as 11COOH, 11CONH2 and 11CH2NH2 into PET probes. [11C]Cyanide is generally prepared by heating [11C]CH4 under NH3 gas flow at more than 900°C in a column filled with platinum. The traditional method, however, requires an additional system for [11C]cyanide production. In this study, we explored a facile method to prepare [11C]cyanide without any special equipment, reagents and conditions. Hooker et al. reported that [11C]HCHO is readily prepared with Me3NO from [11C]MeI in DMF.[1] Augustine et al. reported that alkyl- and aryl-aldehydes can be efficiently converted to corresponding nitriles using NH2OH‧HCl in DMSO.[2] Based on these reports, we investigated the applicability of Augustine’s reaction to [11C]cyanide preparation from [11C]MeI which is commonly used for 11C-labelling.Methods. To a 50 μL of [11C]MeI solution in DMF or DMSO (30–50 MBq), a 50 μL of saturated Me3NO (<2 mg) in DMSO was added. Saturated NH2OH‧HCl solution in DMSO (<10 mg, 100μL) was subsequently added to the reaction mixture. To investigate the effect of HCl addition, 10 μL of 4M HCl/dioxane was added immediately or 2 min after the addition of NH2OH‧HCl. The reaction conditions are summarized in Table 1. Radiochemical yields (average of n=2) were determined by radio-HPLC analysis of the reaction solution.Results. In all reactions, [11C]MeI and [11C]HCHO were almost completely consumed, and [11C]H2CNOH and [11C]cyanide were observed as the major products at the end of reaction. The addition of HCl enhanced dehydration of [11C]H2CNOH to form [11C]cyanide (Entry 1, 3). The timing of HCl addition was important to obtain good yields of [11C]cyanide (Entry 3, 5). Efficient dehydration required heating at >90°C (Entry 2–5). Based on these results, [11C]MeI, NH2OH‧HCl and HCl were serially mixed in a DMSO solution of Me3NO and reacted at 90°C (Entry 6, 7). Despite a report indicating that DMSO is not a suitable solvent for [11C]HCHO preparation from [11C]MeI,[1] we performed a DMF-free [11C]cyanide preparation experiment. This produced [11C]cyanide in 81% radiochemical yield after 10 min reaction time.Conclusion. We have developed a facile method for efficient [11C]cyanide preparation using conventional lab-ware. Further optimization of reaction conditions and the application of the [11C]cyanide prepared with this method are in progress.[1] J. M. Hooker, Matthias Schönberger, H. Schieferstein, J. S. Fowler, Angew. Chem. Int. Ed. 2008, 47, 5989–5992.[2] J. K. Augustine, A. Bombrun, R. N. Atta, Synlett, 2011, 15, 2223–2227. Introduction. [11C]Cyanide has been used as a useful intermediate for incorporation of 11C-labelled functional groups such as 11COOH, 11CONH2 and 11CH2NH2 into PET probes. [11C]Cyanide is generally prepared by heating [11C]CH4 under NH3 gas flow at more than 900°C in a column filled with platinum. The traditional method, however, requires an additional system for [11C]cyanide production. In this study, we explored a facile method to prepare [11C]cyanide without any special equipment, reagents and conditions. Hooker et al. reported that [11C]HCHO is readily prepared with Me3NO from [11C]MeI in DMF.[1] Augustine et al. reported that alkyl- and aryl-aldehydes can be efficiently converted to corresponding nitriles using NH2OH‧HCl in DMSO.[2] Based on these reports, we investigated the applicability of Augustine’s reaction to [11C]cyanide preparation from [11C]MeI which is commonly used for 11C-labelling.Methods. To a 50 μL of [11C]MeI solution in DMF or DMSO (30–50 MBq), a 50 μL of saturated Me3NO (<2 mg) in DMSO was added. Saturated NH2OH‧HCl solution in DMSO (<10 mg, 100μL) was subsequently added to the reaction mixture. To investigate the effect of HCl addition, 10 μL of 4M HCl/dioxane was added immediately or 2 min after the addition of NH2OH‧HCl. The reaction conditions are summarized in Table 1. Radiochemical yields (average of n=2) were determined by radio-HPLC analysis of the reaction solution.Results. In all reactions, [11C]MeI and [11C]HCHO were almost completely consumed, and [11C]H2CNOH and [11C]cyanide were observed as the major products at the end of reaction. The addition of HCl enhanced dehydration of [11C]H2CNOH to form [11C]cyanide (Entry 1, 3). The timing of HCl addition was important to obtain good yields of [11C]cyanide (Entry 3, 5). Efficient dehydration required heating at >90°C (Entry 2–5). Based on these results, [11C]MeI, NH2OH‧HCl and HCl were serially mixed in a DMSO solution of Me3NO and reacted at 90°C (Entry 6, 7). Despite a report indicating that DMSO is not a suitable solvent for [11C]HCHO preparation from [11C]MeI,[1] we performed a DMF-free [11C]cyanide preparation experiment. This produced [11C]cyanide in 81% radiochemical yield after 10 min reaction time.Conclusion. We have developed a facile method for efficient [11C]cyanide preparation using conventional lab-ware. Further optimization of reaction conditions and the application of the [11C]cyanide prepared with this method are in progress.[1] J. M. Hooker, Matthias Schönberger, H. Schieferstein, J. S. Fowler, Angew. Chem. Int. Ed. 2008, 47, 5989–5992.[2] J. K. Augustine, A. Bombrun, R. N. Atta, Synlett, 2011, 15, 2223–2227.
22nd International symposium on radiopharmaceutical science

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