A compound of formula I: ** Formula ** in which: R1 and R2 are different and independent groups and are selected from the group consisting of OR3 and N (R3 ') (R3 ") or R1 and R2 are different and they are connected through a single link, and are selected from the group consisting of O and NR3； R3, R3 ', and R3 "are independently selected from the group consisting of H, C1 to C6 alkyl, C1 to C6 alkyl substituted, C3 to C8 cycloalkyl, aryl, substituted aryl, heteroaryl, and substituted heteroaryl R4 and R4 'are: (a) independently selected from the group consisting of H, OH, O (C1 to C6 alkyl), O (C1 alkyl to substituted C6), O (acyl), O (aryl), O (substituted aryl), and halogen； or (b) taken together to form a double bond with O； R5, R6, and R7 are independently selected from the group consisting of H, OH, and OCH3； R8 and R9 are connected through (i) a single link and are CH2 or (ii) a double link and are CH； R15 is selected from the group consisting of C = O, CHOH, and CH2； n is 1 or 2； wherein the substituents for the substituted alkyl are selected from the group consisting of halogen, CN, OH, NO2, amino, aryl, heterocyclic, alkoxy, aryloxy, alkylcarbonyl, alkylcarboxy, and arylthio； and wherein the substituents for the substituted aryl and the substituted heteroaryl are selected from the group consisting of halogen, CN, OH, NO2, amino, alkyl, cycloalkyl, alkenyl, alkynyl, alkoxy, aryloxy, alkyloxy, alkylcarbonyl, alkylcarboxy, aminoalkyl, and arylthio； or a pharmaceutically acceptable salt thereof.Un compuesto de fórmula I: **Fórmula** en la que: R1 y R2 son grupos diferentes e independientes y se seleccionan entre el grupo que consiste en OR3 y N(R3')(R3") o R1 y R2 son diferentes y se conectan a través de un enlace sencillo, y se seleccionan entre el grupo que consiste en O y NR3； R3, R3', y R3" se seleccionan independientemente entre el grupo que consiste en H, alquilo C1 a C6, alquilo C1 a C6 sustituido, cicloalquilo C3 a C8, arilo, arilo sustituido, heteroar
