Certain chemical entities, compositions, and methods

A method of treating cancer in a subject, the method comprising administering to the subject in need thereof a therapeutically effective amount of a compound of Formula III:

• or a pharmaceutically acceptable salt thereof, wherein:
• R5 is chosen from hydrogen, optionally substituted alkyl, optionally substituted cycloalkyl, optionally substituted heterocycloalkyl, optionally substituted aryl, and optionally substituted heteroaryl;
• and
• R6 is chosen from optionally substituted alkyl, optionally substituted cycloalkyl, optionally substituted heterocycloalkyl, optionally substituted aryl, optionally substituted heteroaryl, optionally substituted acyl, optionally substituted alkoxycarbonyl, and —P(═O)(OR7)(OR8), where R7 and R8 are independently chosen from hydrogen and optionally substituted alkyl;
• wherein the cancer is selected from the group consisting of colorectal cancer, liver cancer, lung cancer, breast cancer, prostate cancer, pancreatic cancer, brain cancer, and oral cancer.