title: Oxorhenium(V) and Oxotechnetium(V) Complexes of Cysteine.
abstract: Earlier attempts to obtain technetium complexes with cysteine always resulted in the formation of a product contaminated with polymeric species. A pure product, which could be chemically characterized and adopted for radiopharmaceutical preparation, has now been obtained by using cystine as the precursor of cysteine. This method has been extended to prepare the corresponding rhenium chelate, isolated as the tetraphenylphosphonium salt [Ph(4)P](+)[{ReO(Cys)(2)}(-){HReO(Cys)(2)}].4H(2)O. The X-ray crystal structure of this compound revealed the presence of both neutral and anionic chelated species. In [HReO(Cys)(2)], the cysteine carboxylate moiety is unidentatedly bound to rhenium, while the carboxylic acid of the second cysteine remains as free COOH. The coordination environment around rhenium in the anionic species [ ReO(Cys)(2)(-)] is similar, the only difference being that the uncoordinated carboxylate moiety is present as a COO(-) anion. The thiolate, amine coordination of the ligand with the metal is present in both the chelate units. The compound crystallized in an orthorhombic system with the space group P2(1)2(1)2(1), and having four formula units in each cell. The crystal data are a = 9.700(2) Å, b = 12.836(3) Å, and c = 36.228(3) Å. The rhenium chelate has been structurally correlated with the technetium chelates through comparable spectroscopic and chromatographic data. The technetium-99m analogue of this rhenium chelate exhibited renal tubular transport and renal retention, which makes this radiopharmaceutical useful for evaluation of the clinical status of renal patients.
authors.affiliation: Departments of Nuclear Medicine and Medicinal Chemistry, Indian Institute of Chemical Biology, 4 Raja S. C. Mullick Road, Calcutta 700032, India, and Crystallography and Molecular Biology Division, Saha Institute of Nuclear Physics, 1/AF Bidhan Nagar, Calcutta 700064, India.
authors.forename: Mita
authors.initials: M
authors.lastname: Chatterjee
authors.forename: Basudeb
authors.initials: B
authors.lastname: Achari
authors.forename: Satyabrata
authors.initials: S
authors.lastname: Das
authors.forename: Rahul
authors.initials: R
authors.lastname: Banerjee
authors.forename: Chandana
authors.initials: C
authors.lastname: Chakrabarti
authors.forename: Jiban K.
authors.initials: JK
authors.lastname: Dattagupta
authors.forename: Somenath
authors.initials: S
authors.lastname: Banerjee