Sialyltransferase inhibitors and uses thereof

A compound having the structure of formula (1)

• and pharmaceutically acceptable salts and solvates thereof, wherein,
• n is an integral from 1 to 4;
• A, B, and C are independently a 6-membered saturated or unsaturated carbon cyclic ring, in which the saturated or unsaturated carbon cyclic ring is optionally substituted with one or more fluoro or hydroxy;
• X1 is O, or N;
• R1 is
• R3 is selected from the group consisting of methyl, methoxy, RaCOOH, RaNH2, RaNHC(NH2)=NH, RaSRb,
• or
• R3 and the neighboring carbon and nitrogen atoms are taken together to form a 5-membered heterocyclic ring;
• Ra and Rb are independently H or C1-6 alkyl;
• R2 is COOH, CH(COOH)COOH, or COX2(CH2CH2O)mCH2CH2N3,
• X2 is O or N, and m is an integral from 1 to 4;
• and
• Ar is selected from the group consisting of H,
• Provided that when R2 is COOH, R1 is not