The invention relates to a compound of Formula I or a pharmaceutically acceptable salt thereof: wherein R1 is C1-8 alkyl, C1-8 alkoxy, CN, NO 2 , amino, COOH, COOCH 3 , OH, N 3 , or halogen and R2 is H, OH, C1-8 alkyl, C1-8 alkoxy, C2-C6 alkenyl, halogen, Bn-O-, Bn-optionally substituted, or Ph- optionally substituted.