More active (+)-enantiomer of ITD 1 ,a selective inhibitor of TGFβ/Smad signaling (IC50 values 0.46 μM and 6.90 μM for (+)-ITD 1 and (−)-ITD 1, respectively for TGF-β inhibition) that acts by clearing the type II TGFβ receptor from the cell surface. ITD 1 stimulates the differentiation of cardiomyocytes and promote cardiogenesis in murine embryonic stem cell (mESCs). TGFβ inhibition by the (+)-enantiomer is approximately 15-fold more effective than by its (−)-enantiomer.