Thiostrepton-inspired compounds for treatment of cancer and preparation thereof

A compound having the structure of Formula (IA):

• or a pharmaceutically acceptable salt thereof, wherein:
• R1 is —NH2, —NH(CH3), —O—CH3, or —NH—CH2—C(O)—NH2;
• R2 is —H, —CH3, ═CH2, or ═CH(alkyl);
• R3 is —H, —CH3, ═CH2, or ═CH(alkyl);
• R5 is —C(O)—R1 or —CN;
• Ring A is aryl, heteroaryl, cycloalkyl, or heterocyclyl;
• Ring B is absent or present and, when present, is aryl, heteroaryl, cycloalkyl, or heterocyclyl;
• R4 is hydrogen, a protecting group, —C(O)—CH3, -L′, or -L-Y;
• L′, when present, is a reactive linker moiety;
• L, when present, is a linker moiety;
• Y, when present, is a mitochondrial targeting moiety;
• each is independently a single bond or a double bond;
• and
• any hydrogen atom is optionally replaced with a deuterium.