Patent ID: 7541485

Claim:
A method for preparing a compound of formula (Ia), comprising: a) treating a compound of formula (IIa), with an alkyl chloroformate of formula (III) and a base, to provide a compound of the formula (IVa); b) treating the compound of formula (IVa) with an amine having the formula of or a pharmaceutically acceptable salt thereof; to give a compound of formula (Va); c) deprotecting the amine protecting group of the compound of formula (Va) to give a compound of formula (VIa); and d) treating the compound of formula (VIa) with an acid chloride having the formula of in the presence of a base to give a compound of formula (VIIa); and e) deprotecting the carboxylic acid protecting group of the compound of formula (VIIa) via hydrolysis to give the compound of formula (Ia), wherein: PG 1 is an amine protecting group; PG 2 is a carboxylic acid protecting group; and R 16 is (C 1 -C 6 ) alkyl.