合成路线1

b) The intermediate 7(S)-(tert-Butoxycarbonylamino)-5-azaspiro[2.4]heptane (VII) can also be obtained as follows: 1) The cyclopropanation of ethyl acetoacetate (XXXI) with 1,2-dibromoethane (XXXII) by means of K2CO3 in DMF gives 1-acetylcyclopropane-1-carboxylic acid ethyl ester (XXXIII), which is brominated with Br2 in ethanol yielding the bromoacetyl derivative (XXXIV). The cyclization of (XXXI) with (R)-alpha-methylbenzylamine (XIII) by means of triethylamine affords 5-[1(R)-phenylethyl]-5-azaspiro[2.4]heptane-4,7-dione (XXXV), which by reaction with hydroxylamine is converted into the monooxime (XXXVI). The reduction of (XXXVI) with H2 over RaNi in methanol affords 7-amino-5-[1(R)-phenylethyl]-5-azaspiro[2.4]heptan-4-one as a diastereomeric mixture (XXXVII) + (XXXVIII), which is separated by column chromatography. The reduction of the (7S)-isomer (XXXVIII) with LiAlH4 in THF gives 7(S)-amino-5-[1(R)-phenylethyl]-5-azaspiro[2.4]heptane (XXXIX), which is protected in the usual way to the tert-butoxycarbonyl derivative (XL). Finally, this compound is debenzylated to (VII) by hydrogenation with H2 over Pd/C in ethanol.