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Z. Naturforsch. 2013,
68b, 739 – 742
doi:10.5560/ZNB.2013-3082
Cobalt(III)-Binding of Gluconate and 2-Amino-2-Deoxy-Gluconate
Department Chemie der Ludwig-Maximilians-Universität, Butenandtstraße 5–13, D-81377 München, Germany
Reprint requests to Prof. Dr. P. Klüfers. Fax: ++49-89-2180-77407. E-mail:
kluef@cup.uni-muenchen.de
Received March 6, 2013 / published online Juli 2, 2013
Dedicated to Professor Heinrich Nöth on the occasion of his 85th birthday
Two isomers of the [Co(tren)(d-Glc1A1,2H−2-κ2O1,2)]+ (1) chelate are formed in equal parts in the reaction of [Co(tren)Cl2]Cl and sodium gluconate. In contrast, the gluconate's 2-amino-2-deoxy derivative glucosaminate formed a single isomer of [Co(tren)(d-Glc1A2N1H−1-κ2N, O2)]2+ (2). Crystals of the OC-6-34 isomer of 1, [1a]PF6 ·H2O, showed the support of the metal-binding site by intramolecular hydrogen bonds. Due to the inertness of the cobalt(III) chelates, spectroscopy on redissolved crystals of
[1a]PF6 ·H2O allowed the separation of the two 13C NMR signal sets of the isomeric mixture. In a DFT approach, a small energy difference explained the formation of two isomers in the case of the gluconate. A larger difference was obtained for the glucosaminate, in line with the known rules for the stereospecific amino acid-Co(tren) chelation.
Key words: Gluconate, 2-Amino-2-deoxy-gluconate, Glucosaminate, Cobalt(III)