Purine compounds possessing anticancer activity

A compound of Formula (I′):

• or a pharmaceutically acceptable salt thereof,
• wherein:
• Z1 is independently Cl, N, O, or S, as valency permits;
• h1 is 0, 1, or 2;
• R1 is
• in which G1 is independently halogen, —CN, —NO2, —N3, optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted carbocyclyl, optionally substituted aryl, optionally substituted heterocyclyl, optionally substituted heteroaryl, —ORA, —SRA, —NHRB, —N(RB)2, —C(═O)RA, —C(═O)ORA, —OC(═O)RA, —C(═O)NHRB, —C(═O)N(RB)2, —NRBC(═O)RA, —OC(═O)N(RB)2, —NRBC(═O)ORA, —NRBC(═O)N(RB)2, —S(═O)RA, —OS(═O)2RA, —SO2RA, —NRBSO2RA, or —SO2N(RB)2;
• and m is 1, 2, 3, 4 or 5;
• wherein when Z1 is S, G1 is hydrogen;
• R2 is
• in which each instance of G2 is independently halogen, —CN, —NO2, —N3, optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted carbocyclyl, optionally substituted aryl, optionally substituted heterocyclyl, optionally substituted heteroaryl, —ORA, —SRA, —NHRB, —N(RB)2, —C(═O)RA, —C(═O)ORA, —OC(═O)RA, —C(═O)NHRB, —C(═O)N(RB)2, —NRBC(═O)RA, —OC(═O)N(RB)2, NRBC(═O)ORA, NRBC(═O)N(RB)2, —S(═O)RA, —OS(═O)2RA, —SO2RA, —NRBSO2RA, or —SO2N(RB)2;
• R3 is hydrogen, optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted carbocyclyl, optionally substituted heterocyclyl, optionally substituted aryl, optionally substituted heteroaryl, —CN, —ORA, —SRA, —NHRB, —N(RB)2, —C(═O)RA, —C(═O)ORA, —C(═O)NHRB, —C(═O)N(RB)2, —SO2RA, or two instances of R3 are taken together with Z1 to form optionally substituted heterocyclyl;
• R4a is —C(═NH)NH(ORA), —C(═N(ORA)NH2, —C(═NH)NHN(RB)2, —C(═NHN(RB)2)NH2, or —C(═NH)N(RB)2;
• wherein
• RA is hydrogen or optionally substituted C1-6 alkyl;
• and
• each instance of RB is independently hydrogen, optionally substituted C1-6 alkyl, optionally substituted aryl.