Conduramine F-1 epoxides: synthesis and their glycosidase inhibitory activities

Starting from (±)-7-oxanorbornenone ((±)-14), (±)-(1RS,2RS,3SR,6SR)-6-azidocyclohex-4-en-1,2,3-triol ((±)-24) and (±)-(1RS,2RS,3SR,6RS)-6-azidocyclohex-4-en-1,2,3-triol ((±)-26) were obtained. Epoxidation of the latter cyclohexene derivative gave two epoxides (±)-30 and (±)-31 that were converted into (±)-conduramine F-1 epoxides (±)-10 and (±)-11 and N-substituted derivatives (±)-12 and (±)-13. Compound (±)-(1RS,2SR,3RS,4SR,5RS,6SR)-5-({4-(trifluoromethyl)phenyl]methyl}amino)-7-oxabicyclo4.1.0]heptane-2,3,4-triol ((±)-12c) is a good, non-competitive inhibitor of β-xylosidase from Aspergillus niger (K_i=2.2 μM), and (±)-(1RS,2RS,3SR,4RS,5SR,6SR)-5-{(biphenyl-4-yl)methyl]amino}-7-oxabicyclo4.1.0]heptane-2,3,4-triol ((±)-13d) is a good inhibitor of α-glucosidase from brewer's yeast (K_i=2.8 μM, non-competitive).