A compound of Formula or: or a pharmaceutically acceptable salt thereof, wherein: each instance of R 1 and R 4 is independently selected from the group consisting of hydrogen, carbonyl, silyl, optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted carbocyclyl, optionally substituted heterocyclyl, optionally substituted aryl, and optionally substituted heteroaryl; each instance of R 2 and R 3 is independently selected from the group consisting of hydrogen, halogen, -OH, substituted hydroxyl, -SH, substituted thiol, -NH 2, substituted amino, - CN, -NO 2, carbonyl, silyl, sulfinyl, sulfonyl, optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted carbocyclyl, optionally substituted heterocyclyl, optionally substituted aryl, and optionally substituted heteroaryl; or R 2 and R 3 are joined to form an optionally substituted carbocyclyl or optionally substituted heterocyclyl group; R 5 is hydrogen; R 6 is selected from the group consisting of hydrogen, optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted carbocyclyl, optionally substituted heterocyclyl, optionally substituted aryl, and optionally substituted heteroaryl; R 7 is selected from the group consisting of hydrogen, optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted carbocyclyl, optionally substituted heterocyclyl, optionally substituted aryl, and optionally substituted heteroaryl; R 12 is selected from the group consisting of hydrogen, carbonyl, silyl, optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted carbocyclyl, optionally substituted heterocyclyl, optionally substituted aryl, and optionally substituted heteroaryl; R 13 is selected from the group consisting of halogen, -OH, substituted hydroxyl, -SH, substituted thiol, -NH 2, substituted amino, -CN, -NO 2, carbonyl, silyl, sulfinyl, sulfonyl, optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted carbocyclyl, optionally substituted heterocyclyl, optionally substituted aryl, and optionally substituted heteroaryl; and R 14 is selected from the group consisting of optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted carbocyclyl, optionally substituted heterocyclyl, optionally substituted aryl, and optionally substituted heteroaryl; or R 13 and R 14 are joined to form an optionally substituted carbocyclyl, optionally substituted heterocyclyl, optionally substituted aryl, or optionally substituted heteroaryl group; for use in treating or preventing a proliferative disorder. each instance of R 1 and R 4 is independently selected from the group consisting of hydrogen, carbonyl, silyl, optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted carbocyclyl, optionally substituted heterocyclyl, optionally substituted aryl, and optionally substituted heteroaryl; each instance of R 2 and R 3 is independently selected from the group consisting of hydrogen, halogen, -OH, substituted hydroxyl, -SH, substituted thiol, -NH 2, substituted amino, - CN, -NO 2, carbonyl, silyl, sulfinyl, sulfonyl, optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted carbocyclyl, optionally substituted heterocyclyl, optionally substituted aryl, and optionally substituted heteroaryl; or R 2 and R 3 are joined to form an optionally substituted carbocyclyl or optionally substituted heterocyclyl group; R 5 is hydrogen; R 6 is selected from the group consisting of hydrogen, optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted carbocyclyl, optionally substituted heterocyclyl, optionally substituted aryl, and optionally substituted heteroaryl; R 7 is selected from the group consisting of hydrogen, optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted carbocyclyl, optionally substituted heterocyclyl, optionally substituted aryl, and optionally substituted heteroaryl; R 12 is selected from the group consisting of hydrogen, carbonyl, silyl, optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted carbocyclyl, optionally substituted heterocyclyl, optionally substituted aryl, and optionally substituted heteroaryl; R 13 is selected from the group consisting of halogen, -OH, substituted hydroxyl, -SH, substituted thiol, -NH 2, substituted amino, -CN, -NO 2, carbonyl, silyl, sulfinyl, sulfonyl, optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted carbocyclyl, optionally substituted heterocyclyl, optionally substituted aryl, and optionally substituted heteroaryl; and R 14 is selected from the group consisting of optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted carbocyclyl, optionally substituted heterocyclyl, optionally substituted aryl, and optionally substituted heteroaryl; or R 13 and R 14 are joined to form an optionally substituted carbocyclyl, optionally substituted heterocyclyl, optionally substituted aryl, or optionally substituted heteroaryl group; for use in treating or preventing a proliferative disorder.