A compound having the structure or a pharmaceutically acceptable salt thereof, wherein R6 is hydrogen, —OH, —C1-6alkyl, —OC1-6alkyl, aryl, or halogen, or together with R7, forms an oxo group, or together with R7 and the atom to which they are attached, form a 5-7-membered carbocycle ring or a 5-7-membered heterocyclic ring having 1, 2, or 3 heteroatoms, wherein alkyl and aryl are unsubstituted or independently mono-, di-, or tri-substituted with R14; R7 is hydrogen, C1-6alkyl, —CF3, aryl, —O-aryl, —O—C1-6alkyl, —C(O)OC1-6alkyl, —C(R15R16)OH, a 5-7-membered heteroaryl having 1, 2, 3 or 4 nitrogen atoms, or halogen, or together with R6, forms an oxo group, or together with R6 and the atom to which they are attached, form a 5-7-membered carbocycle ring or a 5-7-membered heterocyclic ring having 1, 2, or 3 heteroatoms wherein alkyl, aryl and heteroaryl are unsubstituted or independently mono-, di- or tri-substituted with R14; R12 is hydrogen, C1-6alkyl, or —(CH2)1-2OH, or together with R13 and the nitrogen atom to which they are attached, form a 4- to 7-membered heterocyclic ring containing one nitrogen atom and 0 or 1 oxygen atoms, wherein said ring is unsubstituted or independently mono-, di- or tri-substituted with halogen or —C1-6alkyl; R13 is —C1-6alkyl or —(CH2)1-2OH, or together with R12 and the nitrogen atom to which they are attached, form a 4- to 7-membered heterocyclic ring containing one nitrogen atom and 0 or 1 oxygen atoms, wherein said ring is unsubstituted or independently mono-, di- or tri-substituted with halogen or —C1-6alkyl.