Potent 4-aryl- or 4-arylalkyl-substituted 3-isoxazolol GABAA antagonists: Synthesis, pharmacology, and molecular modeling

Bente Frølund; Lars S. Jensen; Luca Guandalini; Carolina Canillo; Henrik T. Vestergaard; Uffe Kristiansen; Birgitte Nielsen; Tine B. Stensbøl; Christian Madsen; Povl Krogsgaard-Larsen; Tommy Liljefors

doi:10.1021/jm049256w

Potent 4-aryl- or 4-arylalkyl-substituted 3-isoxazolol GABA_A antagonists: Synthesis, pharmacology, and molecular modeling

Bente Frølund^*, Lars S. Jensen, Luca Guandalini, Carolina Canillo, Henrik T. Vestergaard, Uffe Kristiansen, Birgitte Nielsen, Tine B. Stensbøl, Christian Madsen, Povl Krogsgaard-Larsen, Tommy Liljefors

^*Corresponding author af dette arbejde

37 Citationer (Scopus)

Abstract

We have previously described a series of competitive GABA_A antagonists derived from the low-efficacy partial agonist 5-(4-piperidyl)-3- isoxazolol (4-PIOL, 4). The 2-naphthylmethyl analogue, 4-(2-naphthylmethyl)-5- (4-piperidyl)-3-isoxazolol (5), provided affinity for the GABA_A receptor site higher than that of the standard GABA_A receptor antagonist, SR 95531 (3). Molecular modeling studies of these compounds exposed a cavity at the receptor recognition site capable of accommodating aromatic groups of substantial size in the 4-position in the 3-isoxazolol ring. Here we present a series of analogues of 5, with various substituents in different positions in the naphthyl ring system (6a-k), and compounds with aromatic substituents directly attached to the 4-position of the 3-isoxazolol ring (71-n). The compounds have been pharmacologically characterized using receptor-binding assays and electrophysiological whole-cell patch-clamp techniques. All of the tested compounds show affinity for the GABA_A receptor site. While the 5-, 7-, and 8-bromo analogues, 6b-d, showed receptor affinities (K_i = 45, 109, and 80 nM, respectively) comparable with that of 5 (K_i = 49 nM), the 1-bromo analogue, 6a, provided the highest receptor affinity of the series (K_i = 10 nM). Introduction of a series of different substituents in the 1-position in the 2-naphthyl ring system led to compounds, 6c-k, with retained high affinity for the GABA _A receptor (K_i = 16-250 nM). Introduction of a phenyl ring directly into the 4-position on the 3-isoxazolol ring gave a 41-fold increase in affinity relative to that of 4-PIOL. In whole-cell patch-clamp recordings from cultured cerebral cortical neurons, all of the tested compounds were able to inhibit the effect of the specific GABA_A agonist isoguvacine, 6a showing antagonist potency (IC₅₀ = 42 nM) markedly higher than that of 3 (IC₅₀ = 240 nM). Molecular modeling studies, based on the compounds described, emphasized the importance of the distal ring in 5 for receptor affinity and the considerable dimensions of the proposed receptor cavity. Furthermore, the phenyl rings in 71 and in 6k were shown to represent highly favorable positions for an aromatic ring in previously unexplored receptor regions in terms of a pharmacophore model.

Originalsprog	Engelsk
Tidsskrift	Journal of Medicinal Chemistry
Vol/bind	48
Udgave nummer	2
Sider (fra-til)	427-439
Antal sider	13
ISSN	0022-2623
DOI	https://doi.org/10.1021/jm049256w
Status	Udgivet - 27 jan. 2005

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Citationsformater

Frølund, B., Jensen, L. S., Guandalini, L., Canillo, C., Vestergaard, H. T., Kristiansen, U., Nielsen, B., Stensbøl, T. B., Madsen, C., Krogsgaard-Larsen, P., & Liljefors, T. (2005). Potent 4-aryl- or 4-arylalkyl-substituted 3-isoxazolol GABA_A antagonists: Synthesis, pharmacology, and molecular modeling. Journal of Medicinal Chemistry, 48(2), 427-439. https://doi.org/10.1021/jm049256w

Frølund, B, Jensen, LS, Guandalini, L, Canillo, C, Vestergaard, HT, Kristiansen, U , Nielsen, B, Stensbøl, TB, Madsen, C, Krogsgaard-Larsen, P & Liljefors, T 2005, 'Potent 4-aryl- or 4-arylalkyl-substituted 3-isoxazolol GABA_A antagonists: Synthesis, pharmacology, and molecular modeling', Journal of Medicinal Chemistry, bind 48, nr. 2, s. 427-439. https://doi.org/10.1021/jm049256w

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title = "Potent 4-aryl- or 4-arylalkyl-substituted 3-isoxazolol GABAA antagonists: Synthesis, pharmacology, and molecular modeling",

abstract = "We have previously described a series of competitive GABAA antagonists derived from the low-efficacy partial agonist 5-(4-piperidyl)-3- isoxazolol (4-PIOL, 4). The 2-naphthylmethyl analogue, 4-(2-naphthylmethyl)-5- (4-piperidyl)-3-isoxazolol (5), provided affinity for the GABAA receptor site higher than that of the standard GABAA receptor antagonist, SR 95531 (3). Molecular modeling studies of these compounds exposed a cavity at the receptor recognition site capable of accommodating aromatic groups of substantial size in the 4-position in the 3-isoxazolol ring. Here we present a series of analogues of 5, with various substituents in different positions in the naphthyl ring system (6a-k), and compounds with aromatic substituents directly attached to the 4-position of the 3-isoxazolol ring (71-n). The compounds have been pharmacologically characterized using receptor-binding assays and electrophysiological whole-cell patch-clamp techniques. All of the tested compounds show affinity for the GABAA receptor site. While the 5-, 7-, and 8-bromo analogues, 6b-d, showed receptor affinities (Ki = 45, 109, and 80 nM, respectively) comparable with that of 5 (Ki = 49 nM), the 1-bromo analogue, 6a, provided the highest receptor affinity of the series (Ki = 10 nM). Introduction of a series of different substituents in the 1-position in the 2-naphthyl ring system led to compounds, 6c-k, with retained high affinity for the GABA A receptor (Ki = 16-250 nM). Introduction of a phenyl ring directly into the 4-position on the 3-isoxazolol ring gave a 41-fold increase in affinity relative to that of 4-PIOL. In whole-cell patch-clamp recordings from cultured cerebral cortical neurons, all of the tested compounds were able to inhibit the effect of the specific GABAA agonist isoguvacine, 6a showing antagonist potency (IC50 = 42 nM) markedly higher than that of 3 (IC50 = 240 nM). Molecular modeling studies, based on the compounds described, emphasized the importance of the distal ring in 5 for receptor affinity and the considerable dimensions of the proposed receptor cavity. Furthermore, the phenyl rings in 71 and in 6k were shown to represent highly favorable positions for an aromatic ring in previously unexplored receptor regions in terms of a pharmacophore model.",

author = "Bente Fr{\o}lund and Jensen, {Lars S.} and Luca Guandalini and Carolina Canillo and Vestergaard, {Henrik T.} and Uffe Kristiansen and Birgitte Nielsen and Stensb{\o}l, {Tine B.} and Christian Madsen and Povl Krogsgaard-Larsen and Tommy Liljefors",

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doi = "10.1021/jm049256w",

language = "English",

volume = "48",

pages = "427--439",

journal = "Journal of Medicinal Chemistry",

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T1 - Potent 4-aryl- or 4-arylalkyl-substituted 3-isoxazolol GABAA antagonists

T2 - Synthesis, pharmacology, and molecular modeling

AU - Frølund, Bente

AU - Jensen, Lars S.

AU - Guandalini, Luca

AU - Canillo, Carolina

AU - Vestergaard, Henrik T.

AU - Kristiansen, Uffe

AU - Nielsen, Birgitte

AU - Stensbøl, Tine B.

AU - Madsen, Christian

AU - Krogsgaard-Larsen, Povl

AU - Liljefors, Tommy

PY - 2005/1/27

Y1 - 2005/1/27

N2 - We have previously described a series of competitive GABAA antagonists derived from the low-efficacy partial agonist 5-(4-piperidyl)-3- isoxazolol (4-PIOL, 4). The 2-naphthylmethyl analogue, 4-(2-naphthylmethyl)-5- (4-piperidyl)-3-isoxazolol (5), provided affinity for the GABAA receptor site higher than that of the standard GABAA receptor antagonist, SR 95531 (3). Molecular modeling studies of these compounds exposed a cavity at the receptor recognition site capable of accommodating aromatic groups of substantial size in the 4-position in the 3-isoxazolol ring. Here we present a series of analogues of 5, with various substituents in different positions in the naphthyl ring system (6a-k), and compounds with aromatic substituents directly attached to the 4-position of the 3-isoxazolol ring (71-n). The compounds have been pharmacologically characterized using receptor-binding assays and electrophysiological whole-cell patch-clamp techniques. All of the tested compounds show affinity for the GABAA receptor site. While the 5-, 7-, and 8-bromo analogues, 6b-d, showed receptor affinities (Ki = 45, 109, and 80 nM, respectively) comparable with that of 5 (Ki = 49 nM), the 1-bromo analogue, 6a, provided the highest receptor affinity of the series (Ki = 10 nM). Introduction of a series of different substituents in the 1-position in the 2-naphthyl ring system led to compounds, 6c-k, with retained high affinity for the GABA A receptor (Ki = 16-250 nM). Introduction of a phenyl ring directly into the 4-position on the 3-isoxazolol ring gave a 41-fold increase in affinity relative to that of 4-PIOL. In whole-cell patch-clamp recordings from cultured cerebral cortical neurons, all of the tested compounds were able to inhibit the effect of the specific GABAA agonist isoguvacine, 6a showing antagonist potency (IC50 = 42 nM) markedly higher than that of 3 (IC50 = 240 nM). Molecular modeling studies, based on the compounds described, emphasized the importance of the distal ring in 5 for receptor affinity and the considerable dimensions of the proposed receptor cavity. Furthermore, the phenyl rings in 71 and in 6k were shown to represent highly favorable positions for an aromatic ring in previously unexplored receptor regions in terms of a pharmacophore model.

AB - We have previously described a series of competitive GABAA antagonists derived from the low-efficacy partial agonist 5-(4-piperidyl)-3- isoxazolol (4-PIOL, 4). The 2-naphthylmethyl analogue, 4-(2-naphthylmethyl)-5- (4-piperidyl)-3-isoxazolol (5), provided affinity for the GABAA receptor site higher than that of the standard GABAA receptor antagonist, SR 95531 (3). Molecular modeling studies of these compounds exposed a cavity at the receptor recognition site capable of accommodating aromatic groups of substantial size in the 4-position in the 3-isoxazolol ring. Here we present a series of analogues of 5, with various substituents in different positions in the naphthyl ring system (6a-k), and compounds with aromatic substituents directly attached to the 4-position of the 3-isoxazolol ring (71-n). The compounds have been pharmacologically characterized using receptor-binding assays and electrophysiological whole-cell patch-clamp techniques. All of the tested compounds show affinity for the GABAA receptor site. While the 5-, 7-, and 8-bromo analogues, 6b-d, showed receptor affinities (Ki = 45, 109, and 80 nM, respectively) comparable with that of 5 (Ki = 49 nM), the 1-bromo analogue, 6a, provided the highest receptor affinity of the series (Ki = 10 nM). Introduction of a series of different substituents in the 1-position in the 2-naphthyl ring system led to compounds, 6c-k, with retained high affinity for the GABA A receptor (Ki = 16-250 nM). Introduction of a phenyl ring directly into the 4-position on the 3-isoxazolol ring gave a 41-fold increase in affinity relative to that of 4-PIOL. In whole-cell patch-clamp recordings from cultured cerebral cortical neurons, all of the tested compounds were able to inhibit the effect of the specific GABAA agonist isoguvacine, 6a showing antagonist potency (IC50 = 42 nM) markedly higher than that of 3 (IC50 = 240 nM). Molecular modeling studies, based on the compounds described, emphasized the importance of the distal ring in 5 for receptor affinity and the considerable dimensions of the proposed receptor cavity. Furthermore, the phenyl rings in 71 and in 6k were shown to represent highly favorable positions for an aromatic ring in previously unexplored receptor regions in terms of a pharmacophore model.

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