2999396

GABA agonists. Resolution, absolute stereochemistry, and enantioselectivity of (S)-(+)- and (R)-(-)-dihydromuscimol.

Article date: 1985/11/1

PubMed ID: 2999396

Journal name: Journal of medicinal chemistry (ISSN: 0022-2623)

ABSTRACT

(RS)-5-(Aminomethyl)-2-isoxazolin-3-ol (dihydromuscimol, DHM) is a potent 4-aminobutyric acid (GABA) agonist, the inhibitory effects of which on neurons are sensitive to the antagonist bicuculline methochloride (BMC), and it also interacts with the GABA uptake system in vitro. (S)-(+)-DHM (4) and (R)-(-)-DHM (5) were obtained in optically pure forms via resolution of tert-butyloxycarbonyl-protected DHM (1) using cinchonidine as the only resolving agent. The optical purity and absolute stereochemistry of 4 and 5 were established by chemical correlation to the (S)-(+) enantiomer of 3-hydroxy-4-aminobutyric acid (GABOB). While 4 was a specific and potent BMC-sensitive GABA agonist in vivo and in vitro, possibly the most potent GABA agonist so far described, the inhibition of GABA uptake by DHM proved to reside exclusively in the (R)-(-) enantiomer (5). The affinity of 5 for BMC-sensitive GABA receptor sites in vitro was some 50 times lower than that of 4. Compounds 4 and 5 can be considered semirigid isosteres of the conformationally flexible GABA analogues (S)-(+)- and (R)-(-)-GABOB, respectively, which show a very low degree of enantioselectivity with respect to GABA synaptic mechanisms. This correlation between the degree of enantioselectivity and conformational mobility of chiral GABA analogues might be of importance for the design of new drugs with specific actions at synapses at which GABA is the transmitter.

This document is available from: http://directlinks.cc/files/muscimol/2999396.pdf

Author List: Krogsgaard-Larsen P, Nielsen L, Falch E, Curtis D R

Publication Types: Comparative Study; Journal Article; Research Support, Non-U.S. Gov't

Substances mentioned in the article: Isoxazoles; Oxazolidinones; Piperidines; Receptors, GABA-A; 4-amino-3-hydroxybutyric acid; Muscimol; gamma-Aminobutyric Acid; dihydromuscimol; piperidine-4-sulfonic acid; bicuculline methochloride; gaboxadol; Diazepam; Bicuculline;

Mesh terms: Animals; Bicuculline/analogs & derivatives; Brain/drug effects; Cats; Chemical Phenomena; Chemistry; Diazepam/metabolism; Isoxazoles/metabolism; Molecular Conformation; Muscimol/analogs & derivatives; Neurons/drug effects; Oxazolidinones; Piperidines/metabolism; Rats; Receptors, GABA-A/drug effects; Spinal Cord/cytology; Stereoisomerism; Structure-Activity Relationship; Synaptic Membranes/metabolism; gamma-Aminobutyric Acid/analogs & derivatives;

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