Solid-phase synthesis of protected peptides using new cobalt(III) ammine linkers.
Cobalt(III) ammine complexes of the type cis-[CoL4(4-AMB)O-AA-Boc](CF3SO3)2, where L4 = bisethylenediamine (en)2 or tetraammine (NH3)4, and 4-AMB = 4-(aminomethyl)benzoic acid, have been synthesized and used as linkers to polystyrene resins for solid-phase synthesis of protected peptides. Boc/t-Bu-protected [Leu5]enkephalin was assembled on the two different Co(III) resins, and then cleaved from the resins by reduction of the Co(III) center in 93-96% yield. HPLC-purified protected [Leu5]enkephalin was obtained in 67-69% overall yield and characterized by amino acid analysis and 1H NMR. Stepwise synthesis on the Co(en)2-resin was also used in the assembly of Boc-Asp(OcHex)-Arg(Mts)-Gly-Asp(OcHex)-Ala-Pro-Lys(2Cl-Z)-Gl y-OH, a sequence from collagen alpha 1 Type 1. The protected peptide was cleaved from the Co(III) resin in 74% yield, and the HPLC-purified nonapeptide was characterized by amino acid analysis, 1H NMR and liquid secondary-ion mass spectrometry (LSIMS). New routes are described for the synthesis of isomerically pure Co(III) anchor complexes. The Co(III) resins were found to be compatible with both the tert-butyloxycarbonyl (Boc) and the 9-fluorenylmethoxycarbonyl (Fmoc) N alpha-protecting group strategies used in solid-phase peptide synthesis.
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Department of Chemistry, Rutgers, State University of New Jersey, Piscataway.
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D000595:Amino Acid Sequence; D003035:Cobalt / Q000737:chemistry*; D003094:Collagen / Q000737:chemistry; D004743:Enkephalin, Leucine / Q000138:chemical synthesis; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000138:chemical synthesis*; D010084:Oxidation-Reduction; D011137:Polystyrenes / Q000737:chemistry
D009842:Oligopeptides; D011137:Polystyrenes; C030862:cobalt ammonium complex; D003035:Cobalt; D004743:Enkephalin, Leucine; D003094:Collagen