Total synthesis of lindbladione, a Hes1 dimerization inhibitor and neural stem cell activator isolated from Lindbladia tubulina.

Lindbladione (1) is a neural stem cell differentiation activator isolated from Lindbladia tubulina by our group. Hes1 dimerization inhibitory activity of lindbladione (1) was discovered using our original fluorescent Hes1 dimer microplate assay. We also found that lindbladione (1) accelerates the differentiation of neural stem cells. We conducted the first total synthesis of lindbladione (1) via Heck reaction of 1-hexene-3-one 7 with iodinated naphthoquinone 12, which was provided by Friedel-Crafts acylation followed by Claisen condensation, in the presence of Pd (II) acetate. Careful deprotection of the benzyl groups of 13 successively provided lindbladione (1). Synthesized lindbladione (1) exhibited potent Hes1 dimer inhibition (IC50 of 2.7 µM) in our previously developed fluorescent Hes1 dimer microplate assay. Synthesized lindbladione (1) also accelerated the differentiation of C17.2 mouse neural stem cells into neurons dose dependently, increasing the number of neurons by 59% (2.5 µM) and 112% (10 µM) compared to the control. These activities are comparable to those of naturally occurring lindbladione (1) isolated from L. tublina.