The reaction of 2-(phthalimido)glutaric acid (I) with acetic anhydride and SOCl2 gives 2-(phthalimido)glutaric anhydride (II), which is treated with urea at 180 C to yield the target thalidomide. Alternatively, anhydride (II) can also be treated with ammonia in dioxane at 180 C in a pressure vessel.
A new scaleable two-step synthesis of thalidomide was reported: The reaction of L-glutamine (I) with N-(ethoxycarbonyl)phthalimide (II) gives the N-phthaloyl-L-glutamine (III), which is finally cyclized by means of carbonyldimidazole (CDI) and dimethylaminopyridine.
A new direct synthesis of thalidomide has been reported: Reaction of the commercially available N-phthaloyl-L-glutamic acid (I) with either urea (II) or thiourea (III) under microwave irradiation (1000 W output) provides thalidomide in 63 or 85% yield, respectively.
A novel solid-phase synthesis of thalidomide has been described: The coupling of phthalic anhydride (I) with hydroxymethyl polystyrene resin (II) by means of triethylamine and 4-dimethylaminopyridine (DMAP) in DMF affords the resin-linked acid (III), which is then condensed with alpha-aminoglutarimide (IV) by means of diisopropylcarbodiimide (DIC) and N-hydroxybenzotriazole (HOBt) in DMF to provide amide (V). Finally, thalidomide is obtained by treatment of resin (V) with TFA in refluxing toluene.
The esterification of N-(tert-butoxycarbonyl)-D-glutamic acid 5-O-benzyl ester (I) with phenol by means of DCC and pyridine in ethyl acetate gives the mixed ester (II), which is treated with H2 over Pd/C in methanol to yield the N-(tert-butoxycarbonyl)-D-glutamic acid 1-O-phenyl ester (III). The cyclization of (III) with O-benzylhydroxylamine (IV) by means of EDC, HOBT and TEA in dichloromethane affords N-[1-(benzyloxy)-2,6-dioxopiperidin-3(R)-yl]carbamic acid tert-butyl ester (V), which is treated with HCl gas in dichloromethane to provide 3(R)-amino-1-(benzyloxy)piperidine-2,6-dione (VI). The reaction of (VI) with phthalic anhydride (VII) by means of TEA in THF gives the phthalimido derivative (VIII), which is debenzylated with H2 over Pd/C in methanol to yield 1-hydroxy-3-(R)-(phthalimido)piperidine-2,6-dione (IX). Finally, the OH group of (IX) is eliminated by reaction with phenacyl bromide (X) and TEA in acetonitrile to afford the phenacyl ether (XI), which is submitted to a nucleophilic cleavage by means of DMAP as the base to obtain the target (R)-thalidomide.
The esterification of N-(tert-butoxycarbonyl)-L-glutamic acid 5-O-benzyl ester (I) with phenol by means of DCC and pyridine in ethyl acetate gives the mixed ester (II), which is treated with H2 over Pd/C in methanol to yield the N-(tert-butoxycarbonyl)-L-glutamic acid 1-O-phenyl ester (III). The cyclization of (III) with O-benzylhydroxylamine (IV) by means of EDC, HOBT and TEA in dichloromethane affords N-[1-(benzyloxy)-2,6-dioxopiperidin-3(S)-yl]carbamic acid tert-butyl ester (V), which is treated with HCl gas in dichloromethane to provide 3(S)-amino-1-(benzyloxy)piperidine-2,6-dione (VI). The reaction of (VI) with phthalic anhydride (VII) by means of TEA in THF gives the phthalimido derivative (VIII), which is debenzylated with H2 over Pd/C in methanol to yield 1-hydroxy-3-(S)-(phthalimido)piperidine-2,6-dione (IX). Finally the OH group of (IX) is eliminated by reaction with phenacyl bromide (X) and TEA in acetonitrile to afford the phenacyl ether (XI), which is submitted to a nucleophilic cleavage by means of DMAP as the base to obtain the target (S)-thalidomide. Alternatively, the phthalimido derivative (VIII) can also be obtained by reaction of 2(S)-(phthalimido)glutaric anhydride (XII) with O-benzylhydroxylamine (IV) by means of DCC and pyridine in dichloromethane.