Synthesis and utilization of 13C and 15N backbone-labeled proline: NMR study of synthesized oxytocin with backbone-labeled C-terminal tripeptide amide.
The 13C and 15N backbone-labeled proline was prepared using Oppolzer's method based on application of a sultam as chiral auxiliary. This isotopomer was used in the synthesis of the 13C, 15N backbone-labeled C-terminal tripeptide amide fragment of neurohypophyseal hormone oxytocin. Finally, this tripeptide amide was coupled by segment condensation with N-Boc- or N-Fmoc-tocinoic acid, followed by N-deprotection with TFA or piperidine. The labeled oxytocin exhibited biological activity identical with that of natural oxytocin. A detailed 1H, 13C and 15N NMR study confirmed the assigned oxytocin conformation containing a beta-turn in the cyclic part of the molecule, stabilized by H-bond(s) that can be perturbed by the C-terminal tripeptide amide moiety as indicated by comparison of NMR data for both the tocine ring in oxytocin and tocinoic acid.
Budesínský
M
M
Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Prague, Czech Republic.
Ragnarsson
U
U
Lankiewicz
L
L
Grehn
L
L
Slaninová
J
J
Hlavácek
J
J
D002247:Carbon Isotopes; D007553:Isotope Labeling / Q000379:methods*; D009075:MSH Release-Inhibiting Hormone / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry; D009587:Nitrogen Isotopes; D019906:Nuclear Magnetic Resonance, Biomolecular; D010121:Oxytocin / Q000138:chemical synthesis*; D011392:Proline / Q000737:chemistry*
D002247:Carbon Isotopes; D009587:Nitrogen Isotopes; C055207:prolyl-leucyl-glycine; D010121:Oxytocin; D009075:MSH Release-Inhibiting Hormone; D011392:Proline