Stereoselective Synthesis of C-2 Alkylated Trihydroxypiperidines: Novel Pharmacological Chaperones for Gaucher Disease.

Pharmacological chaperones (PCs) are small molecules that bind and stabilize enzymes. They can rescue the enzymatic activity of misfolded or deficient enzymes when they are used at subinhibitory concentration, thus with minimal side effects. Pharmacological Chaperone Therapy (PCT) is an emerging treatment for many lysosomal storage disorders (LSDs) including Gaucher disease, the most common, which is characterized by a deficiency in the GCase enzyme. We report herein a straightforward synthetic strategy to afford C-2 substituted trihydroxypiperidines with different alkyl chains starting from low cost d-mannose. Stereoselective Grignard reagent addition onto a key nitrone intermediate in the presence or absence of a suitable Lewis acid afforded both epimers of the target compounds, after a final reductive amination-ring closure step. We show that the shift of the alkyl chain from the endocyclic nitrogen to the C-2 position leads to a considerable increase in chaperoning efficacy, affording a new compound (4a) able to induce a remarkable 1.9-fold maximal increase in GCase activity.