The present invention relates to compounds of formula 1 or pharmaceutically acceptable salts thereof, wherein one of R1 and R2 is methyl, ethyl or isopropyl, and the other is H; R3 and R4 are each independently H, branched or unbranched C1-C6 alkyl, or aryl, and wherein at least one of R3 and R4 is other than H; R5 is a branched or unbranched C1-C5 alkyl group or a C1-C6 cycloalkyl group, each of which may be optionally substituted with one or more OH groups; R6, R7, R8 and R9 are each independently H, halogen, NO2, OH, OMe, CN, NH2, COOH, CONH2, or SO2NH2. A further aspect of the invention relates to pharmaceutical compositions comprising compounds of formula 1, and the use of said compounds in treating proliferative disorders, viral disorders, stroke, alopecia, CNS disorders, neurodegenerative disorders, or diabetes.