Patent ID: 7459556

Claim:
A process for preparing a compound having the structural formula I or a pharmaceutically acceptable salt thereof, R is benzyl, -benzyl-R 5 , allyl, —C(O)R 6 , —C(O)OR 8 or —CH(R 7 ) 2 ; each R 7 is independently selected from the group consisting of -phenyl-R 2 or R 2 -heteroaryl; R 1 is R 3 -aryl, R 3 -heteroaryl, R 3 -arylalkyl- or R 3 -heteroarylalkyl-; R 2 is 1 to 3 substituents independently selected from the group consisting of hydrogen, halogen, alkyl, hydroxy and alkoxy; R 3 is 1-3 substituents independently selected from the group consisting of hydrogen, halogen and alkyl; R 5 is 1 or 2 substituents independently selected from the group consisting of halogen, alkoxy and —NO 2 ; R 6 is H, alkyl, haloalkyl or benzyl; and R 8 is alkyl, benzyl or allyl; comprising a)reacting an amine of formula II R—NH 2 II wherein R is as defined above, with 2,5-dimethoxytetrahydrofuran or HC(O)(CH 2 ) 2 C(O)H, and with C(O)(CH 2 C(O)OR 4 ) 2 , wherein R 4 is H or alkyl, in a buffer, optionally in the presence of a base, to obtain a compound of formula III b) reacting a compound of formula III with I-R 1 , wherein R 1 is as defined above, with alkyl lithium, optionally in the presence of a lithium salt, to obtain a compound of formula I; c) optionally converting a compound of formula I wherein R is benzyl, -benzyl-R 5 , allyl, —C(O)R 6 or —C(O)OR 8 to a compound of formula I wherein R is —CH(R 7 ) 2 by i) reacting the compound of Formula III with a suitable reagent to remove the benzyl, -benzyl-R 5 , allyl, —C(O)R 6 or —C(O)OR 8 group to obtain a compound of formula I(c)(i) and ii) reacting the compound of I(c)(i) or a salt thereof with a compound of formula IV CH(R 7 ) 2 —X IV wherein X is halogen, —OSO 2 CH 3 or —O-(p-toluenesulfonyl) thereby yielding the compound of formula I wherein R is —CH(R 7 ) 2 ; and d) optionally recrystallizing the product of step b) or step c) to obtain a purified product.