Cyclization in situ of enose-/ynose-nitrilimines: an expedient approach to the synthesis of chiral glycopyrazoles and pyrazolonucleosides
摘要:
Intramolecular [3 + 2] nitrilimine cycloaddition reactions on carbohydrate-derived substrates proceed in a regioselective fashion, affording structurally novel chiral glycopyrazoles (4-6 and 10a-c) in good yields. The products can be subsequently transformed to bicyclic pyrazoles (viz. 11 from 4) or nucleoside analogues (viz. 12 from 4). (C) 2004 Elsevier Ltd. All rights reserved.