Cyclization in situ of enose-/ynose-nitrilimines: an expedient approach to the synthesis of chiral glycopyrazoles and pyrazolonucleosides

Intramolecular [3+2] nitrilimine cycloaddition reactions on carbohydrate-derived substrates proceed in a regioselective fashion, affording structurally novel chiral glycopyrazoles ( and ) in good yields. The products can be subsequently transformed to bicyclic pyrazoles (viz. from ) or nucleoside analogues (viz. from ).