Patent ID: 7605258

Claim:
A process for preparing an individual isomer of mono-pegylated rapamycin 42 ester with 3-hydroxy-2-(hydroxymethyl)-2-methylpropionic acid (CCI-779), said process comprising: (a) reacting with HY—(CH 2 CH 2 O) n CH 3 , wherein: X is a leaving group, Y is S or O, R is a protecting group, and n is an integer from 5 to 450; (b) protecting the alcohol group of the product of (a); (c) deprotecting the acid group of the product of (b); (d) resolving the isomers of (c) using a chiral amine or a chiral alcohol; (e) reacting one resolved isomer of (d) with rapamycin; and (f) deprotecting the product of (e).