Concise process for preparing 3-pyrrolidine carboxylic acid derivatives

A process for preparing compound of formula IV:

• wherein
• R1 and R2 are each independently hydrogen, C1-7-alkyl, C3-7-cycloalkyl, halo-C1-7-alkyl, C1-7-alkoxy-C1-7-alkyl, aryl-C1-7-alkyl, or heteroaryl-C1-7-alkyl;
• or
• R1 and R2 together form —(CH2)n—, and n is 2 to 6;
• R3 is hydrogen, C1-7-alkyl, C3-7-cycloalkyl, halo-C1-7-alkyl, C1-7-alkoxy-C1-7-alkyl, aryl-C1-7-alkyl, or heteroaryl-C1-7-alkyl;
• R4 is hydrogen, C1-7-alkyl, C3-7-cycloalkyl, halo-C1-7-alkyl, C1-7-alkoxy-C1-7-alkyl, aryl-C1-7-alkyl, or heteroaryl-C1-7-alkyl;
• and
• R5 is hydrogen, C1-7-alkyl, C3-7-cycloalkyl, halo-C1-7-alkyl, C1-7-alkoxy-C1-7-alkyl, aryl-C1-7-alkyl, or heteroaryl-C1-7-alkyl;
• or a pharmaceutically acceptable salt thereof, which process comprises
• step A:
• reacting compound of formula II:
• wherein R1 and R2 are as defined above, with compound of formula III:
• wherein R3, R4 and R5 are as defined above, in the presence of at least one of compound X which is selected from the group consisting of:
• to obtain compound of formula IV.