Aziridine containing DNA alkylating agents

A compound selected from:

• or a pharmaceutically acceptable salt thereof, or a pharmaceutically acceptable solvate of each thereof, wherein
• R1 is hydrogen, —N3, CN, NR21R22, —OR23, —SO2(C1-C6 alkyl), C1-C6 alkyl, C2-C6 alkenyl, C2-C6 alkynyl, C3-C8 cycloalkyl, C6-C10 aryl, 4-15 membered heterocycle, 5-15 membered heteroaryl, or ether;
• each R21 and R22 independently is hydrogen, hydroxy, C1-C6 alkyl, C2-C6 alkenyl, C2-C6 alkynyl, C3-C8 cycloalkyl, C6-C10 aryl, 4-15 membered heterocycle, 5-15 membered heteroaryl, or —SO2(C1-C6 alkyl);
• or R21 and R22 together with the nitrogen atom they are bonded to form a 4-15 membered heterocycle or a 5-15 membered heteroaryl;
• R23 is hydrogen or C1-C6 alkyl;
• R2 is hydrogen or halo;
• R3 is hydrogen;
• R4 is hydrogen, halo, C1-C6 alkoxy, C1-C6 alkyl, or C6-C10 aryl,
• R5 is hydrogen, C1-C6 alkyl, C2-C6 alkenyl, C2-C6 alkynyl, C3-C8 cycloalkyl, C6-C10 aryl, 4-15 membered heterocycle, 5-15 membered heteroaryl;
• or R4 and R5 together with the intervening carbon atoms between them form a C5-C6 cycloalkyl ring;
• wherein the alkyl, alkenyl, alkynyl, cycloalkyl, aryl, heterocycle, heteroaryl, alkoxy and ether groups are optionally substituted.