| abstract |
A compound of the Formula I in which each R is independently hydrogen or C1-C6 alkyl; R1 and R2 are independently hydrogen, C1-C6 alkyl, OH, - (CH2) n-aryl, (CH2) n-aryl substituted, (CH2) nO-aryl, (CH2) nO-substituted aryl, (CH2) nS- aryl, (CH2) nS-substituted aryl, (CH2) nS-heteroaryl, (CH2) nS-substituted heteroaryl, (CH2) n-NR¿-aryl, (CH2) n-NR¿-substituted aryl, (CH2) n -NR¿-heteroaryl, (CH2) n-NR¿-substituted heteroaryl, (CH2) n-heteroaryl, or (CH2) n-heteroaryl substituted; each n is independently from 0 to 6; R 3 is hydrogen or C1-C6 alkyl; R 4 is C1-C6 alkyl or hydrogen; and X is hydrogen. |