Proton pump inhibitors

A compound of formula (I):

• wherein X1 is CH;
• wherein R1, R2, R3, and R4 are each independently hydrogen, lower alkyl, halogen, hydroxy, alkyloxy, aryl, aryloxy, heteroaryl, trifluoromethoxy, cyano, nitro, thio, alkylthio or a bone targeting moiety, wherein said bone targeting moiety is selected from:
• wherein each occurence of M is independently CV2, —NV—, —O—or —S—, wherein each occurrence of V is independently hydrogen, OH, halogen, or aliphatic;
• each occurrence of Y is independently a covalent bond, —O—, —S—or N(Rj)2, wherein Rj, for each occurrence, is independently hydrogen, aliphatic, heteroaliphatic, aryl, heteroaryl, alkylaryl, or alkylheteroaryl;
• each occurrence of x is independently 0-6, and for compounds i-vi, xi, and xvii, x may preferably be 1-6;
• wherein L is —(CH2)p—He—(CH2)n—, wherein He is absent or is NR', O or S, wherein R' is hydrogen or lower alkyl, n is 0-5, and p is 0-5, except when He is absent, the sum of n and p is 1-5;
• wherein L2 is N or CRK, wherein Rk is hydrogen, aliphatic, heteroaliphatic, aryl, heteroaryl, alkylaryl, or alkylheteroaryl;
• wherein each occurrence of R5 id independently hydrogen or lower alkyl, with the proviso that if either of R2 or R4 are bone targeting moieties, He, for the bone targeting moiety at R2 or R4, is NR', O, or S, wherein R' is hydrogen or lower alkyl;
• wherein R13 represents 0-3 substituents selected from hydrogen, halogen, lower alkyl, lower alkenyl, aryl, heteroaryl, carbonyl, thiocarbonyl, ketone, aldehyde, amino, acylamino, amido, amidino, cyano, nitro, azido, sulfonyl, sulfoxido, sulfate, sulfonate, sulfamoyl, sulfonamido, phosphoryl, phosphorothioate, phosphonate, phosphinate, —(CH2)t-alkyl-, —(CH2)talkenyl-, (CH2)talkynyl-, —(CH2)taryl-, —(CH2)taralkyl-, —(CH2)tOH—, —(CH2)tO-lower alkyl-, (CH2)t)-lower alkenyl, —O(CH2)tR, —(CH2)tS-lower alkyl, —(CH2)tS-lower alkenyl, —S(CH2)tR, —(CH2)tNR2, —(CH2)tNR-lower alkyl, —(CH2)tNR-lower alkenyl, —NR(CH2)tR, or protected forms of the above, and wherein t is 1-10;
• wherein He is:
• wherein R6 and R7 are each independently selected form the group consisting of bone targeting moiety as described above, hydrogen, lower alkyl, substituted or unsubstituted aryl, and substituted or unsubstituted heteroaryl;
• or wherein R6 and R7 taken together, comprise a substituted or unsubstituted aryl, heteroaryl, or cycloalkyl moiety, wherein said substituted or unsubstituted aryl, heteroaryl, or cycloalkyl moiety is a single ring or is polycyclic;
• wherein X2 comprises NR8 or S, wherein R8 is hydrogen, lower alkyl, substituted or unsubstitued aryl, or substituted or unsubstituted heteroaryl;
• and
• whereby at least one of R1-R4, R6, or R7 is substituted with a bone targeting moiety.