Use of a compound of formula or a pharmaceutically acceptable salt thereof for preparation of a medicament for treating cancer in a subject wherein the compound of formula has the structure: wherein R 1 is H, alkyl, -OR, amino, sulfonamido, sulfamido, -OC R 5, - N(R 5)C R 5, or a sugar; R 2 is H, alkyl, alkenyl, alkynyl, aryl, cycloalkyl, nitrile, or heterocycloalkyl; or R 1 and R 2 taken together form =O, =S, =N, =N -, =N(NR 2), =C 2; R 3 is H, alkyl, alkenyl, or alkynyl; R 4 is H, alkyl, alkenyl, alkynyl, aryl, cycloalkyl, heterocycloalkyl, aralkyl, heteroaryl, heteroaralkyl, haloalkyl, -OR 5, -C R 5, -CO 2 R 5, -SO 2 R 5, -C N(R 5)(R 5), -[C 2] q -R 5, -[ -N C] q R 5, -[ -C] q R 5, -[ -C O] q R 5, -[ -OC] q R 5, -[ -SO 2] q R 5, -[ -N(R 5)SO 2] q R 5, -[ -C N(R 5)] q R 5, -[ -O] q R 5, -[ -N] q R 5, -W-NR 5 3 + X -, or -[ -S] q R 5; wherein each W is, independently, a diradical; each q is, independently, 1, 2, 3, 4, 5, or 6; X - is a halide; each R 5 is, independently, H, alkyl, alkenyl, alkynyl, aryl, cycloalkyl, heterocycloalkyl, aralkyl, heteroaryl, heteroaralkyl or -[C 2] p -R 6; wherein p is 0-6; or any two occurrences of R 5 on the same substituent can be taken together to form a 4-8 membered optionally substituted ring which contains 0-3 heteroatoms selected from N, O, S, and P; each R 6 is, independently, hydroxyl, -N COR, -N C OR, -N SO 2, -C N 2, -OC N, -SO 2 N, -N, -COOR, -C N, -OS 2 OR, -S 2 OR, -OP, -NP, or -P; wherein each R is independently H, alkyl, alkenyl, alkynyl, aryl, cycloalkyl or aralkyl; each of R 7 and R 7' is H; or R 7 and R 7' taken together form =O; R 8 and R 9 are H or R 8 and R 9 taken together form a bond; and provided that when R 3, R 4, R 8, R 9 are H and, R 7 and R 7' taken together form =O; R 1 cannot be hydroxyl and R 2 cannot be H; provided that when R 3, R 4, R 8, R 9 are H and, R 7 and R 7' taken together form =O; R 1 cannot be acetate and R 2 cannot be H; provided that when R 3, R 4, R 8, R 9 are H and, R 7 and R 7' are H; R 1 and R 2 taken together cannot be =O; and provided that when R 3, R 4, R 8, R 9 are H and, R 7 and R 7' are H; R 1 and R 2 cannot be H; and wherein the cancer is selected from the group consisting of skin cancer, cancer of the gastrointestinal tract, cancer of the pulmonary system, genitourinary cancer, breast cancer, hepatocellular cancer, brain cancer, ovarian cancer, soft-tissue sarcoma, and cancer of the hematopoietic system. wherein R 1 is H, alkyl, -OR, amino, sulfonamido, sulfamido, -OC R 5, - N(R 5)C R 5, or a sugar; R 2 is H, alkyl, alkenyl, alkynyl, aryl, cycloalkyl, nitrile, or heterocycloalkyl; or R 1 and R 2 taken together form =O, =S, =N, =N -, =N(NR 2), =C 2; R 3 is H, alkyl, alkenyl, or alkynyl; R 4 is H, alkyl, alkenyl, alkynyl, aryl, cycloalkyl, heterocycloalkyl, aralkyl, heteroaryl, heteroaralkyl, haloalkyl, -OR 5, -C R 5, -CO 2 R 5, -SO 2 R 5, -C N(R 5)(R 5), -[C 2] q -R 5, -[ -N C] q R 5, -[ -C] q R 5, -[ -C O] q R 5, -[ -OC] q R 5, -[ -SO 2] q R 5, -[ -N(R 5)SO 2] q R 5, -[ -C N(R 5)] q R 5, -[ -O] q R 5, -[ -N] q R 5, -W-NR 5 3 + X -, or -[ -S] q R 5; wherein each W is, independently, a diradical; each q is, independently, 1, 2, 3, 4, 5, or 6; X - is a halide; each R 5 is, independently, H, alkyl, alkenyl, alkynyl, aryl, cycloalkyl, heterocycloalkyl, aralkyl, heteroaryl, heteroaralkyl or -[C 2] p -R 6; wherein p is 0-6; or any two occurrences of R 5 on the same substituent can be taken together to form a 4-8 membered optionally substituted ring which contains 0-3 heteroatoms selected from N, O, S, and P; each R 6 is, independently, hydroxyl, -N COR, -N C OR, -N SO 2, -C N 2, -OC N, -SO 2 N, -N, -COOR, -C N, -OS 2 OR, -S 2 OR, -OP, -NP, or -P; wherein each R is independently H, alkyl, alkenyl, alkynyl, aryl, cycloalkyl or aralkyl; each of R 7 and R 7' is H; or R 7 and R 7' taken together form =O; R 8 and R 9 are H or R 8 and R 9 taken together form a bond; and provided that when R 3, R 4, R 8, R 9 are H and, R 7 and R 7' taken together form =O; R 1 cannot be hydroxyl and R 2 cannot be H; provided that when R 3, R 4, R 8, R 9 are H and, R 7 and R 7' taken together form =O; R 1 cannot be acetate and R 2 cannot be H; provided that when R 3, R 4, R 8, R 9 are H and, R 7 and R 7' are H; R 1 and R 2 taken together cannot be =O; and provided that when R 3, R 4, R 8, R 9 are H and, R 7 and R 7' are H; R 1 and R 2 cannot be H; and wherein the cancer is selected from the group consisting of skin cancer, cancer of the gastrointestinal tract, cancer of the pulmonary system, genitourinary cancer, breast cancer, hepatocellular cancer, brain cancer, ovarian cancer, soft-tissue sarcoma, and cancer of the hematopoietic system.