Synthesis of enantiomerically pure hydroxylated pyrroline N-oxides from d-ribose
摘要:
A convenient way to obtain enantiomerically pure hydroxylated pyrroline N-oxides is reported. The key step is the formation of omega-oxo criciates from (D)-ribose and a subsequent 1,3-azaprotio cyclotransfer reaction of the resulting oximino alkenoate derivatives. The stereochemistry of the nitrones obtained is discussed in relation to that of the starting compounds. (c) 2006 Elsevier Ltd. All rights reserved.
1,3-Dipolar cycloadditions of different hydrophobic nitrones 1, 2, 3, 4 with acrylates 5 and 6 were studied in both homogenous organic solutions and aqueous suspensions. Reactions in water suspensions showed great rate accelerations over homogenous solutions. Small changes were also observed to the stereoselectivities of the reactions. Hydrophobic interactions are invoked for the observed behaviour.