Certain chemical entities, compositions, and methods

A compound of Formula I:

• or a pharmaceutically acceptable salt thereof, wherein:
• R1, R2, R3, R5, R6, R9, R10, R11 and R12 are independently chosen from hydrogen, hydroxy, optionally substituted alkyl, optionally substituted cycloalkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted alkoxy, optionally substituted aryloxy, optionally substituted heteroaryloxy, optionally substituted heterocycloalkyloxy, optionally substituted aminocarbonyloxy, optionally substituted acyloxy, optionally substituted alkoxycarbonyloxy, and optionally substituted amino;
• or
• R1 and R2, or R5 and R6, or R9 and R10, or R11 and R12 mutually independently, together in each case denote an oxo group (═O);
• R4 is hydroxy, or R4 and R5 may optionally be joined together with any intervening atoms to form an oxirane ring;
• R7 is chosen from hydrogen, hydroxy, optionally substituted alkoxy, optionally substituted aryloxy, optionally substituted heteroaryloxy, optionally substituted heterocycloalkyloxy, optionally substituted aminocarbonyloxy, optionally substituted acyloxy, optionally substituted alkoxycarbonyloxy, and optionally substituted amino;
• R8 is chosen from hydrogen, optionally substituted alkyl, optionally substituted cycloalkyl, optionally substituted alkenyl, and optionally substituted alkynyl;
• or
• R7 and R8 together denote an oxo group (=O);
• R13 is chosen from hydrogen, optionally substituted alkyl, and formyl;
• Z is OR14 or NR15R16;
• R14 is alkyl substituted with optionally substituted heterocycloalkyl;
• R15 is hydrogen;
• R16 is chosen from optionally substituted alkyl, optionally substituted cycloalkyl, or optionally substituted heterocycloalkyl;
• W1 is chosen from:
• W2 is chosen from hydrogen, optionally substituted alkyl, optionally substituted cycloalkyl, optionally substituted alkenyl, and optionally substituted alkynyl;
• n is selected from 0 and 1;
• and
• represents a single bond or a double bond;
• provided that when R4 is OH, R13 is methyl, W1 is
• (2-oxo-2H-pyran-5-yl), and R1, R2, R3, R5, R6, R7, R8, R9, R10, R11, and W2 are hydrogen then R12 is not hydrogen;
• and
• when Z is NR15R16, R4 and R5 are joined together with any intervening atoms to form an oxirane ring.