[Tc(CO)3]+ chemistry: a promising new concept for SPECT?

issue, the reducing agent may be. Analogous to Sn(II), boranocarbonate, as used in the preparation of [99mTc (OH2)3(CO)3], can reduce disulfide bonds. However, under typical reaction conditions amides are not reduced and biomolecules not susceptible to reduction could be labeled in a single step from [TcO4]. This is surprising since stabilization of intermediate valencies such as Tc(IV) by tridentate ligands, leading to side products, could be expected but has not been found. Thus, a onestep reaction for routine application can be achieved, and kit preparation of a 99mTc labeled vector is feasible. From a chemical standpoint, the convenience of preparing [Tc(OH2)3(CO)3] in a kit, its clean reaction with a multitude of free or biomolecule-coupled ligands at room temperature (10−4 M) or at 100°C (10−6 M) to yield chemically and biologically stable complexes, and the possibility of selecting ligands from the bench are the most important arguments in favor of the carbonyl approach. Although discussed in the context of free ligands, these properties also apply to chelator-derivatized biomolecules. The carbonyl approach is feasible and inexpensive and an increasing number of groups have stepped into this new field. Accepting an organometallic moiety as a versatile precursor seems difficult. It is essential to recognize that the organometallic nature of [Tc(OH2)3(CO)3] is the origin of many of the arguments in favor, and coordination compounds may not exhibit the observed behavior. This fact will hopefully encourage research into other organometallic cores for life science. Admittedly, there is still a lack of biological data to support the value, or even the superiority, of the carbonyl approach in radiopharmacy. Comparative studies are required to prove or disprove its complementarity with the other major labeling techniques. Finally, it should be emphasized that while to consider the carbonyl approach as the only solution would be incorrect, its many advantages, as outlined here, open up novel possibilities. Regardless of the success of carbonyls in radiopharmaceutical chemistry, the research leading to [Tc(OH2)3(CO)3] was also recognized by the inorganic and organometallic community. Procedures introduced here are likely to be investigated for other transition metals as well. It is an unusual situation in which research from an applied field inspires fundamental chemistry.

在这个问题上，还原剂可能是……类似于二价锡，用于制备[⁹⁹ᵐTc(OH₂)₃(CO)₃]的硼碳酸酯能够还原二硫键。然而，在典型的反应条件下，酰胺不会被还原，并且不易被还原的生物分子可以从[TcO₄]一步标记。这是令人惊讶的，因为人们可能预期三齿配体对中间价态（如Tc(IV)）的稳定作用会导致副产物，但实际上并未发现。因此，可以实现用于常规应用的一步反应，并且⁹⁹ᵐTc标记载体的试剂盒制备是可行的。从化学角度来看，在试剂盒中制备[Tc(OH₂)₃(CO)₃]的便利性、它在室温（10⁻⁴M）或100°C（10⁻⁶M）下与多种游离或与生物分子偶联的配体的清洁反应以产生化学和生物学上稳定的配合物，以及从实验台上选择配体的可能性，是支持羰基方法的最重要论据。尽管是在游离配体的背景下讨论的，但这些性质也适用于螯合剂衍生的生物分子。羰基方法是可行且廉价的，越来越多的研究小组已经涉足这一新领域。接受有机金属部分作为一种通用前体似乎是困难的。必须认识到[Tc(OH₂)₃(CO)₃]的有机金属性质是许多有利论据的根源，而配位化合物可能不会表现出所观察到的行为。这一事实有望鼓励对用于生命科学的其他有机金属核心进行研究。诚然，仍然缺乏生物学数据来支持羰基方法在放射性药物学中的价值，甚至其优越性。需要进行比较研究来证明或反驳它与其他主要标记技术的互补性。最后，应该强调的是，虽然将羰基方法视为唯一的解决方案是不正确的，但如本文所述，它的许多优点开辟了新的可能性。无论羰基在放射性药物化学中的成功与否，导致[Tc(OH₂)₃(CO)₃]的研究也得到了无机和有机金属领域的认可。这里介绍的方法很可能也会针对其他过渡金属进行研究。这是一种不寻常的情况，即应用领域的研究激发了基础化学的发展。