Novel C-ethoxycarbonyl cyclic ketonitrones are synthesized from the Ag- or Cu-catalyzed ring expansion of β-diazo cyclic hydroxylamines. The latter are themselves easily obtained by the addition of lithiated ethyl diazoacetate onto cyclic nitrones. The regioselective metal-catalyzed rearrangement of β-diazo cyclic hydroxylamines proved highly efficient and resulted in a synthetically useful ring expansion
A systematic study of diastereoselective nucleophilic addition of Grignard reagents to six-membered chiral tri-O-benzyl cyclicnitrones is described. With all eight chiral cyclicnitrones and asymmetric reaction conditions in hand, a practical methodology is established for the preparation of diverse 1-deoxyazapyranosides bearing various stereogenic centers.
piperidine analogues of the pyrrolidine alkaloids radicamine A and radicamineB, were prepared from six-membered cyclic nitrones through a concise two-step procedure, i.e., Grignard reagent addition and deprotection. These novel polyhydroxylated piperidine iminosugars were assayed against 10 types of enzymes. Only compound 8 exhibited weak inhibition (IC50 1080 μmol/L) against β-galactosidase from rat