Synthesis of 13-acylamino-huprines: different behavior of diastereomeric 13-methanesulfonamido-huprines on PPA-mediated hydrolysis

Direct catalytic enantioselective Mannich-type reaction of dichloroacetonitrile using bis(imidazoline)-Pd catalysts

The catalytic enantioselective Mannich-type reaction of dichloroacetonitrile with imines has been developed.

Binding of 13-Amidohuprines to Acetylcholinesterase: Exploring the Ligand-Induced Conformational Change of the Gly117-Gly118 Peptide Bond in the Oxyanion Hole

The acetylcholinesterase (AChE) inhibitory activity of a series of 13-amido derivatives of huprine Y, designed to enlarge the occupancy of the catalytic binding site by mimicking the piridone moiety present in (-)-huperzine A, has been assessed. Although both 13-formamido and 13-methanesulfonamido derivatives are more potent human AChE inhibitors than tacrine and (-)-huperzine A, none of them equals the potency of huprine Y. Molecular modeling studies show that the two derivatives effectively trigger the Gly117-Gly118 conformational flip induced upon binding of (-)-huperzine A, leading to a similar pattern of interactions as that formed by the pyridone amido group of (-)-huperzine A. The detrimental effect on the binding affinity relative to the 13-unsubstituted huprine could be ascribed to a sizable deformation cost associated with the ligand-induced peptide flip. This finding can be interpreted as a mechanism selected by evolution to ensure the preorganization of the functionally relevant oxyanion hole in the binding site of AChE, where residues Gly117 and Gly118 play a relevant role in mediating substrate recognition.