Selective neurokinin antagonists

Compound represented by structural formula (I) or a pharmaceutically acceptable salt thereof, wherein Ar and Ar are optionally substituted heteroaryl or optionally substituted phenyl; X is -O-, -S-, -SO-, -SO2-, -NR -, -NCOR - or -NR SO2R ; (a) is selected from the group consisting of (b), (c), (d) and (e); X is -O-, -S- or -NR -; Y is =O, =S or =NR ; Y is H, C1-C6 alkyl, -NR R , -SCH3, R -aryl(CH2)n6-, R -heteroaryl-(CH2)n6-, -(CH2)n6-heterocycloalkyl, -(C1-C3)alkyl-NH-C(O)O(C1-C6)alkyl or -NHC(O)R ; R , R , R and R are H, alkyl, cycloalkyl, -CHF2, -CH2F or -CF3; or R and R , together with the carbon to which they are attached, form an alkylene ring; or R and R together are =O; R is R or -OH; and the remaining variables are as defined in the specification, methods of treating diseases susceptible to treatment with neurokinin antagonists with said compounds. Also disclosed are pharmaceutical compositions comprising an effective amount of a compound of claim 1, at least one pharmaceutically acceptable carrier, and in combination with an effective amount of a selective serotonin reuptake inhibitor.