Synthesis of enantiomeric pyrans from a 3--allylallose derivative by the application of intramolecular nitrone cycloaddition
摘要:
The intramolecular nitrone cycloaddition of three sets of 3-O-allylpyranose and the corresponding homochiral 3-O-allylfuranose-5-aldehyde derivatives was studied; one set derived from D-allose gave rise to only pyran derivatives which were converted to enantiomeric pyranoisoxazolidines via minor degradations.
Cycloaddition of 3-O-allyl-1,2-isopropylidene N-Ph nitrones afforded appreciably increased yields of oxepanes compared to the corresponding N-Me or N-Bn nitrones. Higher yields permitted some useful further transformations of the oxepanes. (c) 2008 Elsevier Ltd. All rights reserved.