1. Design and Synthesis of a Series of l-trans-4-Substituted Prolines as Selective Antagonists for the Ionotropic Glutamate Receptors Including Functional and X-ray Crystallographic Studies of New Subtype Selective Kainic Acid Receptor Subtype 1 (GluK1) Antagonist (2S,4R)-4-(2-Carboxyphenoxy)pyrrolidine-2-carboxylic Acid
Niels Krogsgaard-Larsen, et al. J Med Chem. 2017 Jan 12;60(1):441-457. doi: 10.1021/acs.jmedchem.6b01516. Epub 2016 Dec 22.
Ionotropic glutamate receptor antagonists are valuable tool compounds for studies of neurological pathways in the central nervous system. On the basis of rational ligand design, a new class of selective antagonists, represented by (2S,4R)-4-(2-carboxyphenoxy)pyrrolidine-2-carboxylic acid (1b), for cloned homomeric kainic acid receptors subtype 1 (GluK1) was attained (Ki = 4 μM). In a functional assay, 1b displayed full antagonist activity with IC50 = 6 ± 2 μM. A crystal structure was obtained of 1b when bound in the ligand binding domain of GluK1. A domain opening of 13-14° was seen compared to the structure with glutamate, consistent with 1b being an antagonist. A structure-activity relationship study showed that the chemical nature of the tethering atom (C, O, or S) linking the pyrrolidine ring and the phenyl ring plays a key role in the receptor selectivity profile and that substituents on the phenyl ring are well accommodated by the GluK1 receptor.
2. (1S*,2S*,4R*,5R*)-Cyclo-hexane-1,2,4,5-tetra-carb-oxy-lic acid
Akira Uchida, Masatoshi Hasegawa, Shinya Yamaguchi, Eiichiro Takezawa, Atsushi Ishikawa, Takashi Kagayama Acta Crystallogr Sect E Struct Rep Online. 2013 Dec 21;70(Pt 1):o75. doi: 10.1107/S1600536813033795. eCollection 2014 Jan 1.
The title compound, C10H12O8, a prospective raw material for colourless polyimides which are applied to electronic and microelectronic devices, lies about an inversion centre and the cyclo-hexane ring adopts a chair conformation. Two crystallographycally independent carb-oxy-lic acid groups on adjacent C atoms are in equatorial positions, resulting in a mutually trans conformation. In the crystal, O-H⋯O hydrogen bonds around an inversion centre and a threefold rotoinversion axis, respectively, form an inversion dimer with an R 2 (2)(8) motif and a trimer with an R 3 (3)(12) motif.
