The invention encompasses a novel compound of formula I:(see formula I)its pharmaceutically acceptable salts, hydrates, solvates, clathrates,enantiomers,diastereomers, racemates, or mixtures of stereoisomers, pharmaceuticalcompositions comprising a compound of formula I, wherein R1, R2, X1, X2, X3,X4,Y and Z are as defined herein, and methods of use of the compound of formula Iand compositions comprising thereof in mammals for treatment or prevention ofdiseases associated with unregulated levels of PDE4.