Abstract: This invention is directed to methods of using compounds having the structure: and including stereoisomers, solvates, and pharmaceutically acceptable salts thereof, wherein each of R1, R2, R3 and R4 is independently selected from hydrogen, R5, R6, and R7; R5 is selected from alkyl, heteroalkyl, aryl and heteroaryl; R6 is selected from (R5)n-alkylene, (R5)n-heteroalkylene, (R5)n-arylene and (R5)n-heteroarylene; R7 is selected from (R6)n-alkylene, (R6)n-heteroalkylene, (R6)n-arylene, and (R6)n-heteroarylene; and n is selected from 0, 1, 2, 3, 4 and 5, where R1 and R2 may together form a heterocyclic structure including the nitrogen to which they are both attached, and R3 and R4 may together form a heterocyclic structure including the nitrogen to which they are both attached; and each of L1 and L2 is independently selected from -A1-A2-A3- where each of A1, A2, and A3 is independently selected from a direct bond, alkylene, heteroalkylene, arylene and heteroarylene.