title: Synthesis, characterization, X-ray crystallography, and cytotoxicity of a cymantrene keto carboxylic acid for IR labelling of bioactive peptides on a solid support.
abstract: Cym-CO-CH2-CH2-COOH was prepared in good yield by Friedel-Crafts reaction of cymantrene (Cym, CpMn(CO)3) with succinic anhydride for the IR labelling of peptides and fully characterized, including an X-ray structure analysis (monoclinic space group P2(1)/n, a=5.727(3)A, b=19.865(9)A, c=10.518(5)A, beta=91.211(9) degrees). The compound was isolated in pure form without the need for chromatographic work-up and subsequently used for solution-phase synthesis of a bioconjugate with phenylalanine methyl ester to allow a complete spectroscopic characterization of this model system. The cymantrene keto carboxylic acid also turned out to be a very robust marker in automated microwave-assisted solid phase peptide synthesis (SPPS). [Leu5]-enkephalin (Tyr-Gly-Gly-Phe-Leu) was prepared on a Wang resin and labelled with the cymantrene derivative on the solid support under microwave irradiation in all steps. The metal-carbonyl marker stayed intact during cleavage from the resin with concentrated trifluoroacetic acid. After simple precipitation and lyophilization, the cymantrene-enkephalin bioconjugate could be obtained in analytically pure form without the need of HPLC purification. As required, the compound is non-cytotoxic against MCF-7 cells at up to 100 microM. This protocol thus allows one to introduce organometallic IR spectroscopic labels to peptides in a very straightforward way.
authors.affiliation: Lehrstuhl für Anorganische Chemie I - Bioanorganische Chemie, Ruhr-Universität Bochum, Universitätsstr. 150, D-44801 Bochum, Germany.
authors.forename: Harmel W
authors.initials: HW
authors.lastname: Peindy N'Dongo
authors.forename: Ines
authors.initials: I
authors.lastname: Neundorf
authors.forename: Klaus
authors.initials: K
authors.lastname: Merz
authors.forename: Ulrich
authors.initials: U
authors.lastname: Schatzschneider
mesh_terms: D002264:Carboxylic Acids / Q000737:chemistry; D045744:Cell Line, Tumor; D004745:Enkephalins / Q000737:chemistry; D006801:Humans; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry* / Q000633:toxicity*; D010455:Peptides / Q000138:chemical synthesis* / Q000737:chemistry; D010649:Phenylalanine / Q000031:analogs & derivatives / Q000737:chemistry; D013055:Spectrophotometry, Infrared
chemical_list: D002264:Carboxylic Acids; D004745:Enkephalins; D009942:Organometallic Compounds; D010455:Peptides; C541517:cymantrene keto carboxylic acid; C034515:phenylalanine methyl ester; D010649:Phenylalanine; C044679:manganese cyclopentadienyl tricarbonyl