A compound having formula I. R1, R2, R3 and R4 are independently H or lower alkyl. R5 is aryl, heteroaryl, cycloalkyl, heterocycloalkyl, aryloxy, heteroaryloxy, cycloalkyloxy, heterocycloalkyloxy, arylamino, heteroarylamino, cycloalkylamino, heterocycloalkyl amino, arylthio, heteroarylthio, cycloalkylthio, heterocycloalkylthio, or cyclic olefin, any of which may be substituted or non-substituted; or substituted alkyl, substituted alkyl oxy or substituted alkyl amino wherein the substituent is an aryl, a heteroaryl, a cycloalkyl, a heterocycloalkyl or a cyclic olefin, any of which may be substituted or non-substituted. X is C or N. n and p are independently whole numbers selected from 0, 1 and 2. (CH2)n and (CH2)p may be substituted or non-substituted. Ar1 and Ar2 are independently aryl or heteroaryl groups which may be substituted or non-substituted. Certain specific compounds are excluded.The compounds can be used in a medicament or a method for the reduction or prevention of the emission of sperm, or for the reduction or prevention of transmission of viral agents transmitted in seminal fluid.