Preparation, spectroscopic properties, and structure of 1-oxo-2,3,6-(D-penicillaminato-N,S,O)-4,5-(D-penicillaminato-N,S)technetium(V)

Franklin, Kenneth J.; Howard-Lock, H. E.; Lock, C. J. L.

doi:10.1021/ic00135a046

Cited by 64 publications

(35 citation statements)

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“…The distance of the Tc-O(carboxylate) bond is relatively short (2.010 Ä) compared to that of the trans-coordinated carboxylic group in TcO(pen)2 (pen = penicillamine) (2.214 Ä) [8], which is in accordance with the high stability of the TC-MAG2 observed in the above experiments.…”

Section: Condusionssupporting

confidence: 86%

Occurrence and Nature of Different Tc(V) and Re(V) Complexes with Mercapto/Amide Ligands

et al. 1993

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The ligand exchange reaction of Tc(V) gluconate and Re(V) gluconate was carried out with mercaptoacetyl triglycine (MAG3), mercaptoacetyl diglycine (MAGj) and mercaptoacetyl glycine (MAGi) as well as their methylesters. In dependence on the ligand/metal molar ratio up to three complexes are obtained. A Single X-ray structurc determination was carried out for the tetraphenylarsonium sah of [TcO(MAG2)]". MAG2 methylester and MAG; form 2:1 complexes as the main products.

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Section: Condusionssupporting

confidence: 86%

Occurrence and Nature of Different Tc(V) and Re(V) Complexes with Mercapto/Amide Ligands

et al. 1993

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“…500 nm (anti diastereomers) are assigned to ligand field transitions, similar to spectral data of other characterized TcO 3+ complexes possessing thiolate ligands and square pyramidal coordination. [53][54][55] The bands at ca. 350 nm may be higher energy ligand field bands or CT transitions.…”

Section: Spectroscopic Signatures Of Syn and Anti [Tco]/[reo] Tripeptmentioning

confidence: 99%

MO Tripeptide Diastereomers (M =^99/99^mTc, Re): Models To Identify the Structure of⁹⁹^mTc Peptide Targeted Radiopharmaceuticals

et al. 2007

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Biologically active molecules, such as many peptides, serve as targeting vectors for radiopharmaceuticals based on 99mTc. Tripeptides can be suitable chelates and are easily and conveniently synthesized and linked to peptide targeting vectors through solid-phase peptide synthesis and form stable TcVO complexes. Upon complexation with [TcO]3+, two products form; these are syn and anti diastereomers, and they often have different biological behavior. This is the case with the approved radiopharmaceutical [99mTcO]depreotide ([99mTcO]P829, NeoTect) that is used to image lung cancer. [99mTcO]depreotide indeed exhibits two product peaks in its HPLC profile, but assignment of the product peaks to the diastereomers has proven to be difficult because the metal peptide complex is difficult to crystallize for structural analysis. In this study, we isolated diastereomers of [99TcO] and [ReO] complexes of several tripeptide ligands that model the metal chelator region of [99mTcO]depreotide. Using X-ray crystallography, we observed that the early eluting peak (A) corresponds to the anti diastereomer, where the Tc=O group is on the opposite side of the plane formed by the ligand backbone relative to the pendant groups of the tripeptide ligand, and the later eluting peak (B) corresponds to the syn diastereomer, where the Tc=O group is on the same side of the plane as the residues of the tripeptide. 1H NMR and circular dichroism (CD) spectroscopy report on the metal environment and prove to be diagnostic for syn or anti diastereomers, and we identified characteristic features from these techniques that can be used to assign the diastereomer profile in 99mTc peptide radiopharmaceuticals like [99mTcO]depreotide and in 188Re peptide radiotherapeutic agents. Crystallography, potentiometric titration, and NMR results presented insights into the chemistry occurring under physiological conditions. The tripeptide complexes where lysine is the second amino acid crystallized in a deprotonated metallo-amide form, possessing a short N1-M bond. The pKa measurements of the N1 amine (pKa approximately 5.6) suggested that this amine is rendered more acidic by both metal complexation and the presence of the lysine residue. Furthermore, peptide chelators incorporating a lysine (like the chelator of [TcO]depreotide) likely exist in the deprotonated form in vivo, comprising a neutral metal center. Deprotonation possibly mediates the interconversion process between the syn and anti diastereomers. The N1 amine group on non-lysine-containing metallopeptides is not as acidic (pKa approximately 6.8) and does not deprotonate and crystallize as do the metallo-amide species. Three of the tripeptide ligands (FGC, FSC, and FKC) were radiolabeled with 99mTc, and the individual syn and anti isomers were isolated for biodistribution studies in normal female nude mice. The main organs of uptake were the liver, intestines, and kidneys, with the FGC compounds exhibiting the highest liver uptake. In comparing the diastereomers, the syn compounds had substantially hi...

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“…The ligand atoms bonded to Tc form a rough square pyramid such that the Tc atom lies 0.770 (3)/k above the best S1, N1, N2, $2 plane. The plane is quite distorted, however, with the two N atoms lying about one quarter of an ~,ngstr6m on either side of this plane (8) et al, 1978;Bandoli, Nicolini et al, 1984;Franklin et al, 1982) and much shorter than in Tc IIl complexes [range 2.412 to 2.520(3)A] (Abrams, Davison, Faggiani, Jones & Lock, 1984;Baldas, Bonnyman, Pojer, Williams & MacKay, 1982). Distances within the organic moiety are normal and all angles lie within the ranges of related We acknowledge, with thanks, financial support from the Natural Sciences and Engineering Research Council of Canada.…”

Section: Introductionmentioning

confidence: 99%

(3,6-Dimethyl-3,6-diazaoctan-1,8-dithiolato-S1,N3,N6,S8)oxotechnetium(V) pertechnetate

Faggiani¹,

Lock²,

Epps³

et al. 1988

Acta Crystallogr C

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Preparation, spectroscopic properties, and structure of 1-oxo-2,3,6-(D-penicillaminato-N,S,O)-4,5-(D-penicillaminato-N,S)technetium(V)

Cited by 64 publications

References 1 publication

Occurrence and Nature of Different Tc(V) and Re(V) Complexes with Mercapto/Amide Ligands

Occurrence and Nature of Different Tc(V) and Re(V) Complexes with Mercapto/Amide Ligands

MO Tripeptide Diastereomers (M =^99/99^mTc, Re): Models To Identify the Structure of⁹⁹^mTc Peptide Targeted Radiopharmaceuticals

(3,6-Dimethyl-3,6-diazaoctan-1,8-dithiolato-S1,N3,N6,S8)oxotechnetium(V) pertechnetate

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Preparation, spectroscopic properties, and structure of 1-oxo-2,3,6-(D-penicillaminato-N,S,O)-4,5-(D-penicillaminato-N,S)technetium(V)

Cited by 64 publications

References 1 publication

Occurrence and Nature of Different Tc(V) and Re(V) Complexes with Mercapto/Amide Ligands

Occurrence and Nature of Different Tc(V) and Re(V) Complexes with Mercapto/Amide Ligands

MO Tripeptide Diastereomers (M =99/99mTc, Re): Models To Identify the Structure of99mTc Peptide Targeted Radiopharmaceuticals

(3,6-Dimethyl-3,6-diazaoctan-1,8-dithiolato-S1,N3,N6,S8)oxotechnetium(V) pertechnetate

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MO Tripeptide Diastereomers (M =^99/99^mTc, Re): Models To Identify the Structure of⁹⁹^mTc Peptide Targeted Radiopharmaceuticals