Regio- and stereospecific [3+2] cycloaddition of an unusual nitrone derived from a N-hydroxy-2-pyridone with medium ring enones

Regio- and stereospecific 1,3-dipolar cycloaddition of the nitrone derived from a N-hydroxy-2-pyridone 6 with Z-2-cyclodecenone 7a was accomplished, thus substantiating a possible biomimetic route to pyridomacrolidin 2 from pyridovericin 1 and cephalosporolide B 5. This reaction was further exemplified with different enones (7a-g) similar to cephalosporolide B 5. In all the cases the cycloaddition occurred with high regiochemical control and with high retention of alkene geometry. Both endo and exo modes of cycloaddition were observed. This process can also be extended to aryl conjugated enones as long as no enolisable hydrogens are present. (C) 2004 Elsevier Ltd. All rights reserved.