The cyclopropanation of ethyl acetoacetate (I) with 1,2-dibromoethane and K2CO3 in DMF, followed by hydrolysis with NaOH gives 1-acetylcyclopropane-1-carboxylic acid (II), which is condensed with 1(R)-phenylethylamine (A) by means of butyl chloroformate in dichloromethane yielding the chiral amide (III). The protection of the acetyl group with ethylene glycol and p-toluenesulfonic acid affords the cyclic acetal (IV), which is brominated with Br2 in dioxane to give the bromomethyl compound (V). The cyclization of (V) by means of NaH in THF affords the spirocyclopropane derivative (VI), which is deprotected with HCl providing the spiro pyrrolidinedione (VII). The reaction of (VII) with hydroxylamine affords the oxime (VIII), which is reduced with H2 over RaNi in methanol and crystallized with l-tartaric acid to give the desired chiral 7(R)-amino-5-(1(R)-phenylethyl)-5-azaspiro[2.4]heptan-4-one (IX). The reduction of the ketonic group of (IX) with LiAlH4 yields the chiral amine (X), which is protected with tert-butoxycarbonyl anhydride to the carbamate (XI). The hydrogenation of (XI) with H 2 over Pd/C affords the spiropyrrolidine (XII) with its NH group free, which is condensed with the quinolizine (XIII) by means of triethylamine in DMF providing intermediate (XIV). Finally, this compound is deprotected and hydrolyzed to the target compound with LiOH in ethanol.

The cyclopropanation of ethyl acetoacetate (I) with 1,2-dibromoethane and K2CO3 in DMF, followed by hydrolysis with NaOH gives 1-acetylcyclopropane-1-carboxylic acid (II), which is condensed with 1(R)-phenylethylamine (A) by means of butyl chloroformate in dichloromethane yielding the chiral amide (III). The protection of the acetyl group with ethylene glycol and p-toluenesulfonic acid affords the cyclic acetal (IV), which is brominated with Br2 in dioxane to give the bromomethyl compound (V). The cyclization of (V) by means of NaH in THF affords the spirocyclopropane derivative (VI), which is deprotected with HCl providing the spiro pyrrolidinedione (VII). The reaction of (VII) with hydroxylamine affords the oxime (VIII), which is reduced with H2 over RaNi in methanol and crystallized with l-tartaric acid to give the desired chiral 7(R)-amino-5-(1(R)-phenylethyl)-5-azaspiro[2.4]heptan-4-one (IX). The reduction of the ketonic group of (IX) with LiAlH4 yields the chiral amine (X), which is protected with tert-butoxycarbonyl anhydride to the carbamate (XI). The hydrogenation of (XI) with H 2 over Pd/C affords the spiropyrrolidine (XII) with its NH group free, which is condensed with the quinolizine (XIII) by means of triethylamine in DMF providing intermediate (XIV). This compound is methylated by means of methyl iodide and sodium bis(trimethylsilyl)amide yielding the methylamino derivative (XV), which is finally deprotected and hydrolyzed to the target compound with LiOH in ethanol.