Kojic amine - a novel .gamma.-aminobutyric acid analog

Abstract
A series of compounds containing the 3-hydroxy-4H-pyran-4-one nucleus was synthesized and tested as potential skeletal muscle relaxants. Reduction of 2-(azidomethyl)-5-hydroxy-4H-pyran-4-one (4) with HBr in HOAc-phenol yielded 2-(aminomethyl)-5-hydroxy-4H-pyran-4-one (kojic amine, 3) in 81% yield. Reaction of 2-[(tosyloxy)-methyl]-5(benzyloxy)-4H-pyran-4-one (5) with NH3 gave a 40% yield of the 0-benzyl ether of kojic amine, which was N-acylated with a series of carbobenzyloxy-protected amino acids. Complete deprotection with HBr-HOAc gave the following amino acid amides of kojic amine: glycyl (23), .alpha.-alanyl (24), .beta.-alanyl (25), .gamma.-aminobutyryl (26), and glycylglycyl (27). Among the analogs of kojic amine prepared was a series of one-carbon homologs: 2-[(methylamino)methyl]-5-hydroxy-4H-pyran-4-one (7a), 2-(1-aminoethyl)-5-hydroxy-4H-pyran-4-one (8), 6-(aminomethyl)-3-hydroxy-2-methyl-4H-pyran-4-one (12), and 2-(2-aminoethyl)-5-hydroxy-4H-pyran-4-one (16). Kojic amine (3) possessed certain of the properties to be expected in a GABA mimetic agent, notably skeletal muscle relaxant activity. In the chronic spinal cat preparation, ED70 values for reduction of flexor spasma of 2.2 and 4.0 mg/kg i.v. and p.o. [orally] routes of administration, respectively, were observed for kojic amine, which was the most potent of the various hydroxypyrone derivatives investigated.