Site-Selective Functionalization of Linear Diterpenoids through U-Shaped Folding in a Confined Artificial Cavity.

Even flexible linear substrates are conformationally fixed within the hydrophobic confined cavities of enzymes. This enables preorganization of the substrates and their positioning in close proximity to the active center to facilitate stereo- and site-selective reactions. Here, we demonstrate the site-selective electrophilic addition of linear diterpenoids within a self-assembled coordination cage. The reactions proceed through folding of the linear substrates into a U-shaped conformation, which results in noncovalent protection of internal C═C bonds to enhance the site selectivity.

Catalytic Transfer Hydration of Cyanohydrins to α-Hydroxyamides.

We report the palladium(II)-catalyzed transfer hydration of cyanohydrins to α -hydroxyamides by using carboxamides as water donors. This method enables selective hydration of various aldehyde- and ketone-derived cyanohydrins to afford α-mono- and α,α-disubstituted-α -hydroxyamides, respectively, under mild conditions (50 °C, 10 min). The direct conversion of fenofibrate, a drug bearing a benzophenone moiety, into a functionalized α,α-diaryl-α -hydroxyamide was achieved by means of a hydrocyanation-transfer hydration sequence. Preliminary kinetic studies and the synthesis of a site-specifically 18O-labeled α -hydroxyamide demonstrated the carbonyl oxygen transfer from the carboxamide reagent into the α -hydroxyamide product.