Structure-activity relationships of talaumidin derivatives: Their neurite-outgrowth promotion in vitro and optic nerve regeneration in vivo.

(-)-Talaumidin (1), a 2,5-biaryl-3,4-dimethyltetrahydrofuran lignan, shows potent neurotrophic activities such as neurite-outgrowth promotion and neuroprotection. Previously, we found that (-)-(1S,2R,3S,4R)-stereoisomer 2 exhibited more significant activity than did the natural product talaumidin (1). However, the preparation of optically active (-)-2 requires a complicated synthetic route. To explore new neurotrophic compounds that can be obtained on a large scale, we established a short step synthetic route for talaumidin derivatives and synthesized fourteen analogues based on the structure of (-)-2. First, we synthesized a racemic compound of (-)-2 (2a) and assessed its neurotrophic activity. We found that the neurotrophic property of racemic 2a is similar in activity to that of (-)-2. Using the same synthetic methodology, several talaumidin derivatives were synthesized to optimize the oxy-functionality on aromatic rings. As a result, bis(methylenedioxybenzene) derivative 2b possessed the highest neurotrophic activity. Furthermore, examination of the structure-activity relationships of 2b revealed that the 2,5-diphenyl-tetrahydrofuran structure was an essential structure and that two methyl groups on THF ring could enhance neurotrophic activity. In addition, compounds 2a and 2b were found to induce mouse optic nerve regeneration in vivo.