Amidation process for the preparation of cathepsin K inhibitors

A process for preparing a compound of formula I:

• comprising amidating a salt of formula IIA or an acid of formula IIB
• with 1-aminocyclopropane carbonitrile, in the presence of a coupling agent, wherein the coupling agent is a carbodiimide, a phosphonium salt or a uronium salt;
• a base, wherein the base is N-methyl morpholine, TEA, N-ethyldiisopropylamine, 2,6-lutidine, 2,4,6 collidine or 1-methylpiperidine;
• a solvent, wherein the solvent is DMF, DMAc, NMP, acetonitrile, THF or DMSO;
• and an activating agent;
• wherein R1 is C1-6 alkyl or C1-6 haloalkyl;
• R2 is C1-6 alkyl or C1-6 haloalkyl;
• R3 is SOm(C1-6 alkyl);
• X is a tertiary amine, a secondary amine or a metal salt;
• and
• m is an integer from zero to two.