Combining Bifunctional Chelator with (3 + 2)-Cycloaddition Approaches: Synthesis of Dual-Function Technetium Complexes

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• 作者：Henrik Braband ; Sebastian Imstepf ; Michael Benz ; Bernhard Spingler ; Roger Alberto
• 刊名：Inorganic Chemistry
• 出版年：2012
• 出版时间：April 2, 2012
• 年：2012
• 卷：51
• 期：7
• 页码：4051-4057
• 全文大小：333K
• 年卷期：v.51,no.7(April 2, 2012)
• ISSN：1520-510X

文摘

A new concept for the synthesis of dual-functionalized technetium (Tc) compounds is presented, on the basis of the reactivity of fac-{Tc^VIIO₃}⁺ complexes. The concept combines the 鈥渃lassical鈥?bifunctional chelator (BFC) approach with the new ligand centered labeling strategy of fac-{TcO₃}⁺ complexes with alkenes ((3 + 2)-cycloaddition approach). To evidence this concept, fac-{⁹⁹TcO₃}⁺ model complexes containing functionalized 1,4,7-triazacyclononane (tacn) derivatives N-benzyl-2-(1,4,7-triazonan-1-yl)acetamide (tacn-ba) and 2,2鈥?2鈥?(1,4,7-triazonane-1,4,7-triyl)triacetic acid (nota路3H) were synthesized and characterized. Whereas [⁹⁹TcO₃(tacn-ba)]⁺ [2]⁺ can be synthesized following a established oxidation procedure starting from the Tc^V complex [⁹⁹TcO(glyc)(tacn-ba)]⁺ [1]⁺, a new synthetic pathway for the synthesis of [⁹⁹TcO₃(nota)]^2- [5]^2- had to be developed, starting from [⁹⁹Tc(nota路3H)(CO)₃]⁺ [4]⁺ and using sodium perborate tetrahydrate (NaBO₃路4H₂O) as oxidizing reagent. While [⁹⁹TcO₃(nota)]^2- [5]^2- is a very attractive candidate for the development of trisubstituted novel multifunctional radioprobes, (3 + 2)-cycloaddition reactions of [⁹⁹TcO₃(tacn-ba)]⁺ [2]⁺ with 4-vinylbenzenesulfonate (styrene-SO₃^{鈥?/sup>) demonstrated the suitability of monosubstituted tacn derivatives for the new mixed 鈥淏FC-(3 + 2)-cycloaddition鈥?approach. Kinetic studies of this reaction lead to the conclusion that the alteration of the electronic structure of the nitrogen donors by, e.g., alkylation can be used to tune the rate of the (3 + 2)-cycloaddition.}