A synchronizing device includes a pair of longitudinal guiding units each having a rack member and a movement damper connected to the rack member, and a rotating mechanism including a pair of pinion gears to be meshed respectively with the guiding units. More particularly, the invention provides for compounds of formula, and N-oxides, hydrates, solvates, pharmaceutically acceptable salts, prodrugs and complexes thereof, and racemic and scalemic mixtures, diastereomers and enantiomers thereof, wherein L, M, n, R, W, X and Y are as defined in the specification. Removal of the ball unit is facilitated by a tool-inserting slot at the other end of the U-shaped region.