Studies on the Determination Methods with Polyaldehydes. VIII. : Fluorescence of 2-Phenyl-5, 6-substituted Phthalimidine Derivatives

Reporter Affinity Labels: An o-Phthalaldehyde Derivative of β-Naltrexamine as a Fluorogenic Ligand for Opioid Receptors

“…11 Synthon 8, which was required for coupling to β-naltrexamine (3), was prepared as follows (Scheme 1): 3,4-Dimethylbenzoic acid was converted to its tetrabromo derivative 4 in the presence of N-bromosuccinimide and benzoyl peroxide. 12 Treatment of 4 with a hot aqueous solution of sodium carbonate followed by acidic hydrolysis gave 3,4-diformylbenzoic acid (5). 12 Bis-acetalization of 5 with ethylene glycol under Dean-Stark conditions afforded the carboxylic acid 6.…”

“…12 Treatment of 4 with a hot aqueous solution of sodium carbonate followed by acidic hydrolysis gave 3,4-diformylbenzoic acid (5). 12 Bis-acetalization of 5 with ethylene glycol under Dean-Stark conditions afforded the carboxylic acid 6. Coupling of 6 with glycine ethyl ester in the presence of 1-hydroxybenzotriazole and dicyclohexylcarbodiimide gave the amido ester 7 which was saponified to afford the key intermediate 8.…”

“…Compound 2 (in its hydrated dihydroxyphthalan form) has been synthesized in seven steps from 3,4-dimethylbenzoic acid and β-naltrexamine ( 3 ) . Synthon 8 , which was required for coupling to β-naltrexamine ( 3 ), was prepared as follows (Scheme ): 3,4-Dimethylbenzoic acid was converted to its tetrabromo derivative 4 in the presence of N -bromosuccinimide and benzoyl peroxide . Treatment of 4 with a hot aqueous solution of sodium carbonate followed by acidic hydrolysis gave 3,4-diformylbenzoic acid ( 5 ) .…”