Synthesis of Constrained C‐Glycosyl Amino Acid Derivatives Involving 1,3‐Dipolar Cycloaddition of Cyclic Nitrone as Key Step

An efficient two‐step strategy for the synthesis of constrained C ‐glycosyl amino acid derivatives from C ‐vinylglycosides involving a 1,3‐dipolar cycloaddition using l ‐(–)‐menthone‐derived nitrone as the key step is described. After optimization of 1,3‐dipolar cycloaddition conditions, various C ‐vinylglycosides were tested leading exclusively to one diastereoisomer of the corresponding cycloadduct in good to excellent yields. The total facial selectivity observed was also studied by DFT calculations. Original conformationally restricted C ‐glycosyl amino acid derivatives (8 examples) were isolated after simple cleavage of the chiral auxiliary.