We have designed and synthesized a series of structurally novel hydroxamic acid-based histone deacetylase (HDAC) inhibitors characterized by a zinc chelating head group attached directly to a thiazole ring. The thiazole ring connects to a piperazine spacer, which is capped with a sulfonamide group. These novel molecules potently inhibit an HDAC enzyme mixture derived from HeLa cervical carcinoma cells and show potent antiproliferative activity against the breast cancer cell line MCF7.