The present invention provides a class of compounds, which includes enantiomers and pharmaceutically acceptable salts thereof, that selectively and effectively inhibit Hakai-mediated ubiquitination, preferably without affecting Hakai protein levels, thereby representing excellent anti-cancer drugs useful in the treatment of a variety of cancers, such as carcinomas, in particular, tumors arising from the epithelial layers of the gastrointestinal track including month (oral cancer), esophagus, stomach, and small and large intestines (such as rectal or colon cancer). It also includes skin cancer, mammary gland (breast cancer), pancreas cancer, lung cancer, head and neck cancer, liver cancer, ovary cancer, cervix cancer, uterus cancer, gallbladder cancer, penile cancer, and urinary bladder cancer (such as renal, prostate or bladder cancer).