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
Sugar-derived cyclic nitrones were synthesized from the corresponding aldoses through an efficient and practical procedure involving a seven-step reaction sequence in good to excellent overall yield (10-42%). This synthetic strategy, requiring only inexpensive reagents, is easy to perform and hence suitable for large-scale preparations.
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
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.
NHC-mediated cross-coupling of sugar-derived cyclic nitrones with enals: general and efficient synthesis of polyhydroxylated pyrrolizidines and indolizidines
the synthesis of polyhydroxylated pyrrolizidines and indolizidines has been developed based on the NHC-catalyzed cross-coupling of sugar-derived cyclic nitrones with enals, which afforded the key intermediates, γ-hydroxyl amino esters, in good to excellent yields. Thus, a variety of polyhydroxylated pyrrolizidines and indolizidines have been synthesized and assayed against various glycosidases, which