Process for preparing hydroxypyrrolidinyl ethylamine compounds useful as kappa agonists

A process of preparing a compound in crystalline form having the formula I:

• 19
• or an optical isomer or optically active mixture of two or more stereoisomers thereof, wherein Ar1 and Ar2 are phenyl;
• R1 is hydrogen, hydroxy, C1-C4 alkyl, C1-C4 alkoxy or OY wherein Y is a hydroxy protecting group;
• and
• R2 and R3 are independently selected from hydrogen and C1-C4 alkyl;
• which comprises (a) treating a compound having the formula II:
• 20
• wherein Ar1, Ar2, R1, R2, and R3 are as defined above and R4 is C1-C4 alkyl(C═O)—, aryl(C═O)—, NH2(C═O)—, tri(C1-C4 alkyl)silyl, or triarylsilyl, and having the same stereochemical configuration at the corresponding chiral centers as the compound of formula I, with a base in the presence of an alkyl alcohol, and (b) isolating in crystalline form the compound of formula I.