Beta-substituted beta-amino acids and analogs as chemotherapeutic agents and uses thereof

A compound of Formula (1):

• or a pharmaceutically acceptable salt thereof,
• wherein,
• R1 comprises a first chemotherapeutic moiety;
• R4 is selected from the group consisting of hydrogen and a second chemotherapeutic moiety;
• each of R2, R3, and R5 is hydrogen;
• R6 is selected from the group consisting of —COOH, substituted C1-4 heteroalkyl, substituted C1-4 alkyl, and —PH(═O)(—OH), wherein each substituent group is independently selected from the group consisting of C1-3 alkyl, ═O, and C1-3 alkoxy;
• each R7 is independently selected from the group consisting of hydrogen and hydroxyl;
• R8 is selected from the group consisting of hydrogen and —CH3;
• and
• L is selected from the group consisting of a bond, —CH2—, —CH2—O—, —CH2—CH2—, —CH(—OH)—, —C(═O)—NH—, —C(═O)—N(—CH3)—, and —CH2—C(═O)—,
• wherein each of the first chemotherapeutic moiety and the second chemotherapeutic moiety is independently selected from the group consisting of —N(—CH2—CH2—Cl)2, —N(—CD2-CD2-Cl)2, —N(—CH2—CH2—Br)2, —N(—CH2—CH2—OH)2, —CH2—N(—CH2—CH2—Cl)2, —CH2—C(═O)—N(—CH2—CH2—Cl)2, —O—C(═O)—N(—CH2—CH2—Cl)2, —NH—C(═O)—CH2—Br, —CH2—O—C(═O)—N(—CH2—CH2—Cl)2, —N(—CH2—CH2—Cl)(—CH2—CH2—OH), —N(—O—CH2—CH2—Cl)(—CH2—CH2—Cl), —NH—CH2—CH2—Cl, —NH—CH2—CH2—OH, —N+(—O−)(—CH2—CH2—Cl)2, —N(—CH2—CH2—O—S(═O)2—CH3)2, —N(—CH2—CH2—Cl)(—CH2—CH2—O—S(═O)2—CH3), —N(—CH2—CH2—Br)(—CH2—CH2—O—S(═O)2—CH3), —N(—CH2—CH2—Cl)(—CH2—CH2—Br), and