Conformational study of C8 diazocine turn mimics using {sup 3}J{sub CH} coupling constants with {sup 13}C in natural abundance
- SmithKline Beecham Pharmaceuticals, King of Prussia, PA (United States)
The conformations of two diazocine turn mimics, which were later incorporated into GPIIb/IIIa peptide antagonists, were investigated using nuclear magnetic resonance techniques. The two compounds, methyl (2,5-dioxo-3-(S)-(3-{omega}-tosylguanidino-propyl)-4-methyl-octahydro-1,4-dazocin-1-yl)acetate (1) and methyl (2,5-dioxo-3-(S)-(3-{omega}-tosyl-guanidino-propyl)-octahydro-1,5-diazocin-1-yl)acetate (2), differ only in their substituent at the diazocine position 4 nitrogen, yet this substitution results in a marked difference in the affinity of the resulting analogs for the GPIIb/IIIa receptor. It was of interest to determine if the difference observed in the antagonistic potency between these analogs was related to constitutional or, perhaps, conformational differences. The backbone conformations of these two molecules can be determined by measuring vicinal coupling constants along the trimethylene portion of the C8 ring backbone and by measuring interproton NOE intensities between the diazocine methine proton and the protons of the trimethylene group. For compound 1, {sup 3}J{sub HH} values measured from a P.E.COSY spectrum and interproton distances calculated from ROESY buildup curves indicated the presence of a single C8 ring backbone conformation where the trimethylene bridge adopted a staggered conformation and the H{alpha}1 and H{gamma}1 protons of the trimethylene group were 2.2 A from the methine proton. For compound 2, however, partial overlap of the central H{beta}1 and H{beta}2 protons made it impossible to measure {sup 3}J{sub HH} values from the P.E.COSY spectrum. We therefore used a {sup 13}C-filtered TOCSY experiment to measure the {sup 3}J{sub CH} values in both compounds 1 and 2. These heteronuclear vicinal coupling constants measured with {sup 13}C in natural abundance in conjunction with measured interproton NOE intensities indicate that these compounds share a common C8 ring backbone conformation.
- Research Organization:
- Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
- OSTI ID:
- 83393
- Report Number(s):
- LA-12893-C; CONF-9403228-; ON: DE95012795; TRN: 95:004732-0024
- Resource Relation:
- Conference: Stable isotope applications in biomolecular structure and mechanisms, Santa Fe, NM (United States), 27-31 Mar 1994; Other Information: PBD: Dec 1994; Related Information: Is Part Of Stable isotope applications in biomolecular structure and mechanisms. A meeting to bring together producers and users of stable-isotope-labeled compounds to assess current and future needs; Trewhella, J.; Cross, T.A.; Unkefer, C.J. [eds.]; PB: 382 p.
- Country of Publication:
- United States
- Language:
- English
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