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We report herein the design and synthesis of a series of 5-C-alkyldeoxynojirimycins from l-sorbose, through an efficient and scalable method amenable to preparing a large variety of analogues. The interaction of this class of compounds with human acid α-glucosidase (GAA), the genetically defective enzyme in patients suffering from Pompe disease, was investigated to identify pharmacological chaperones exhibiting high selectivity for this enzyme. Crystallographic analyses provided a rationale for their binding mode to GAA and chaperone activity. The effects of 5-C-phenethyl-DNJ (4c) were evaluated on GAA activity enhancement in cells from Pompe disease patients and in vivo in GAA-KO mice. The significant increase of GAA activity in the presence of 4c in various tissues, particularly in the diaphragm, encourages further studies on this class of small molecules toward developing clinical drugs. Their chaperone activity and excellent selectivity may offer potential benefits over the current treatments for Pompe disease.

Enantiopure (R) and (S) cyclic α,α-disubstituted amino acid derivatives displaying a δ-valerolactam side chain were prepared from a common isoxazolidine precursor. The (R)-configured δ-valerolactam 11 was converted into diastereoisomeric pseudopeptides to investigate its ability to induce secondary structures in peptidomimetics. Conformational studies of these pseudopeptides were carried out in the solid state (X-ray diffraction), in solution (NMR analyses), and in silico (computer-aided conformational analysis), which demonstrated that such quaternary amino acids induce β-turn conformations stable enough to be retained in polar media (DMSO). Incorporation of this new type of α,α-disubstituted amino acid into a representative pseudopeptidic sequence by N- then C-elongation and N-debenzylation is also described herein and could serve for the synthesis of various structured peptidomimetics.

The synthesis of unprecedented branched pyrrolizidines and indolizidines was accomplished via nitrone chemistry. The required ketonitrone, a known intermediate usually obtained as a mixture of regioisomers, was prepared in a pure form from D-arabinose by a sequence of oximation/reduction/oxidation steps. Nucleophilic vinylation or allylation followed by ring-closing metathesis of the corresponding N-allylpyrrolidines furnished the targeted iminosugars, which proved potent and selective inhibitors of alpha-glucosidase from rice (GH31 family).

The synthesis of the peracetylated ketonitrone 4 is described in four steps from L-sorbose. This cyclic nitrone is crystalline and proved to preferentially adopt a ⁴H₃ conformation with all acetate groups in pseudo-axial orientation. Nitrone 4 undergoes regioselective cycloadditions with alkynes, affording tetra-O-acetyl-isoxazolines with good yields and stereoselectivities (4 : 1 to 9 : 1 diastereomeric ratio). Nitrone 4 and the obtained isoxazolines were smoothly deacetylated to produce the polyhydroxylated nitrone 5 and novel iminosugars containing an isoxazoline motif. Evaluation of their glycosidase inhibitory activity demonstrated their rather weak, but selective affinity for a variety of enzymes.

A 1,3‐dipolar cycloaddition reaction of carbohydrate‐derived five‐membered cyclic ketonitrones with alkynes and alkenes was developed as an efficient and regioselective process to access highly functionalised isoxazolines and isoxazolidines bearing a quaternary centre α to the nitrogen atom. The latter compounds were used as intermediates for the synthesis of unprecedented ring‐junction‐substituted polyhydroxylated pyrrolizidines and indolizidines. These compounds were evaluated against a panel of glycosidases, and showed moderate but selective inhibition of α‐glucosidases.

The Baldwin rearrangement is a thermally induced ring contraction of 4‐isoxazolines into 2‐acylaziridines. The reaction yields highly strained nitrogen‐containing three‐membered‐ring compounds from readily available five‐membered N‐O heterocycles. Diversely substituted isoxazolines are directly transformed into a variety of highly functionalized 2‐acylaziridines in a stereocontrolled process. In this review mechanistic aspects and stereoselectivity of this rearrangement are discussed. Although still undervalued, the Baldwin rearrangement may have significant applications in the synthesis of complex aziridine‐containing targets such as natural products or pharmaceuticals.