The present teachings provide compounds of formula I (I) and their pharmaceutically acceptable salts, hydrates, and esters, wherein R<；SUP>；1<；/SUP>；, R<；SUP>；2<；/SUP>；, and X are as defined herein. The present teachings also provide methods of making the compounds of formula I, and methods of treating autoimmune and inflammatory diseases by administering a therapeutically effective amount of a compound or compounds of formula I to a mammal including a human.
