Patent ID: 8916572

Claim:
A compound of formula I or a pharmaceutically acceptable salt thereof, wherein: R 1 and R 2 are each independently —O-alkylene-OCH 3 ; Z is a linker selected from the group consisting of: —O-(alkylene-X 1 ) m -alkylene-(X 2 -alkylene) n -O—, —O-(alkylene-X 1 ) m -cycloalkylene-(X 2 -alkylene) n -O—, and —O-(alkylene-X 1 ) m -heterocyclylene-(X 2 -alkylene) n -O—; X 1 and X 2 , at each occurrence, are independently —O—, —NR 3 —, —S—, —SO—, or —SO 2 —; m and n, at each occurrence, are independently selected from integers from 1 to 10; R 3 is H, —COR 4 , or —SO 2 R 4 ; and R 4 is alkyl or cycloalkyl.