Patent ID: 7417153

Claim:
A method for preparing a compound of formula: and/or mirror image thereof, wherein R 1 is hydrogen, C 1-6 -alkyl, C 3-8 -cycloalkyl or benzyl, and in which (i) R 2 is methyl and R 3 is ethyl, or (ii) R 2 is hydrogen and R 3 is C 1-6 -alkyl or phenyl, or (iii) R 2 is methyl and R 3 is methyl, or (iv) R 2 and R 3 together are a group of the formula —(CH 2 ) n — with n=4 to 6, and which is in the form of a free amine or a salt of a dibasic or tribasic organic acid, comprising: (A) converting a 2-acetyl-2-azabicyclo[2.2.1]hept-5-en-3-one of formula: and/or mirror image thereof, by cis hydroxylation of the double bond into a 2-acetyl-5,6-dihydroxy-2-azabicyclo[2.2.1]heptan-3-one of formula: and/or mirror image thereof, (B) converting the compound of the formula III by reaction with a ketone or an aldehyde of the formula R 2 —CO—R 3 , wherein R 2 and R 3 have the above stated meanings, or by reaction with 2,2-dimethoxypropane or 2,2-dimethoxybutane into a ketal or an acetal of formula: and/or mirror image thereof, wherein R 2 and R 3 have the above stated meanings, (C) converting the ketal or acetal of the formula IV by reductive ring opening into a compound of formula: and/or mirror image thereof, wherein R 2 and R 3 have the above stated meanings, (D) optionally converting the compound of formula V or an alcoholate thereof by reaction with dimethyl sulfate, benzyl chloride or a halide of the formula R 1 —X wherein R 1 has the above stated meaning other than hydrogen, and X is bromine or iodine, into an ether of formula: and/or mirror image thereof, wherein R 1 has the above stated meaning other than hydrogen and R 2 and R 3 have the above stated meanings, (E) converting a compound of the formula V or VI by alkaline hydrolysis into a compound of formula: and/or mirror image thereof, wherein R 1 , R 2 and R 3 have the above stated meanings, and (F) optionally converting the compound of the formula I by addition of a dibasic or tribasic organic acid into corresponding salt wherein R 1 , R 2 and R 3 have the above stated meanings.