A compound of Formula: or a pharmaceutically acceptable salt, stereoisomer, or tautomer thereof, wherein: R 3 is hydrogen, halogen, optionally substituted alkyl, optionally substituted carbocyclyl, optionally substituted heterocyclyl, optionally substituted aryl, or optionally substituted heteroaryl; R 4 is hydrogen, halogen, or optionally substituted alkyl; or R 3 and R 4 are joined to form an optionally substituted carbocyclic or optionally substituted heterocyclic ring; R N is hydrogen, optionally substituted alkyl, optionally substituted acyl, or a nitrogen protecting group; or R N and either R 3 or R 4 are joined to form an optionally substituted heterocyclic ring; R 5 is hydrogen, halogen, optionally substituted alkyl, optionally substituted carbocyclyl, optionally substituted heterocyclyl, optionally substituted aryl, or optionally substituted heteroaryl; R 6 is hydrogen, halogen, optionally substituted alkyl, optionally substituted carbocyclyl, optionally substituted heterocyclyl, optionally substituted aryl, or optionally substituted heteroaryl; or R 5 and R 6 are joined to form an optionally substituted carbocyclic or optionally substituted heterocyclic ring; R 8 is -C(=O)R 8b, optionally substituted alkyl, optionally substituted carbocyclyl, optionally substituted heterocyclyl, -C(=O)OR 8a, -C(=O)N(R 8a) 2, -S(=O) 2 R 8a, or a nitrogen protecting group; each occurrence of R 8a and R 8b is independently hydrogen, optionally substituted alkyl, optionally substituted alkenyl, optionally substituted carbocyclyl, optionally substituted heterocyclyl, optionally substituted aryl, optionally substituted heteroaryl, optionally substituted acyl, an oxygen protecting group, or a nitrogen protecting group, or two R 8a are joined to form an optionally substituted heterocyclic or optionally substituted heteroaryl ring; L 1 is a bond, an amino acid, or a dipeptide; each of R c and R d is independently hydrogen, optionally substituted alkyl, optionally substituted acyl, or a nitrogen protecting group; and each of R A1, R A2, R A3, and R A4 is independently hydrogen, optionally substituted alkyl, optionally substituted acyl, optionally substituted sulfonyl, or a nitrogen protecting group, or any two of R A1, R A2, R A3, and R A4 are joined to form an optionally substituted heterocyclic or optionally substituted heteroaryl ring; provided the compound is not of formula: and with the proviso that the compound is not t-butoxycarbonyl-D-phenylalanylprolyl-ω-N-(benzyloxycarbonyl)arginylfluoromethane. R 3 is hydrogen, halogen, optionally substituted alkyl, optionally substituted carbocyclyl, optionally substituted heterocyclyl, optionally substituted aryl, or optionally substituted heteroaryl; R 4 is hydrogen, halogen, or optionally substituted alkyl; or R 3 and R 4 are joined to form an optionally substituted carbocyclic or optionally substituted heterocyclic ring; R N is hydrogen, optionally substituted alkyl, optionally substituted acyl, or a nitrogen protecting group; or R N and either R 3 or R 4 are joined to form an optionally substituted heterocyclic ring; R 5 is hydrogen, halogen, optionally substituted alkyl, optionally substituted carbocyclyl, optionally substituted heterocyclyl, optionally substituted aryl, or optionally substituted heteroaryl; R 6 is hydrogen, halogen, optionally substituted alkyl, optionally substituted carbocyclyl, optionally substituted heterocyclyl, optionally substituted aryl, or optionally substituted heteroaryl; or R 5 and R 6 are joined to form an optionally substituted carbocyclic or optionally substituted heterocyclic ring; R 8 is -C(=O)R 8b, optionally substituted alkyl, optionally substituted carbocyclyl, optionally substituted heterocyclyl, -C(=O)OR 8a, -C(=O)N(R 8a) 2, -S(=O) 2 R 8a, or a nitrogen protecting group; each occurrence of R 8a and R 8b is independently hydrogen, optionally substituted alkyl, optionally substituted alkenyl, optionally substituted carbocyclyl, optionally substituted heterocyclyl, optionally substituted aryl, optionally substituted heteroaryl, optionally substituted acyl, an oxygen protecting group, or a nitrogen protecting group, or two R 8a are joined to form an optionally substituted heterocyclic or optionally substituted heteroaryl ring; L 1 is a bond, an amino acid, or a dipeptide; each of R c and R d is independently hydrogen, optionally substituted alkyl, optionally substituted acyl, or a nitrogen protecting group; and each of R A1, R A2, R A3, and R A4 is independently hydrogen, optionally substituted alkyl, optionally substituted acyl, optionally substituted sulfonyl, or a nitrogen protecting group, or any two of R A1, R A2, R A3, and R A4 are joined to form an optionally substituted heterocyclic or optionally substituted heteroaryl ring;