Inhibitor of apoptosis (IAP) protein antagonists

A compound or pharmaceutically acceptable salt thereof, having the structure of Formula (A-III):

• wherein,
• X is NRA, O, S, S(O), or S(O)2;
• RA is hydrogen;
• R2a, R2b, R3a, and R3b are each hydrogen;
• R6a is —U;
• R6b is —U;
• —U is C1-C6alkyl;
• or R6a and R6b together with the carbon atom to which they are attached form a saturated or partially saturated 3- to 7-membered cycloalkyl or a saturated or partially saturated 3- to 7-membered heterocycloalkyl;
• R7a is hydrogen;
• R7b is hydrogen;
• R8 is Z, CH(Z)2, CH2CH(Z)2, CH(C1-C6alkyl)Z, or C(O)Z;
• and
• Z is C3-C10cycloalkyl, 3- to 10-membered heterocycloalkyl, C6-C10aryl, or 5- to 10-membered heteroaryl;
• wherein each Z is optionally substituted with 1, 2, or 3 C1-C4alkyl, C1-C4haloalkyl, C1-C4alkoxy, C1-C4haloalkoxy, or 5- to 10-membered heteroaryl provided that when R6a and Rob are both CH3 or when R6a and R6b together with the carbon atom to which they are attached form an unsubstituted cyclopentyl or unsubstituted cyclopentenyl, then R8 is not