Experimental and theoretical studies on stereo- and regioselectivity in intramolecular nitrone-alkene cycloaddition of Hept-6-enoses derived from carbohydrates

Tony K.M. Shing, Annie W.F. Wong, Taketo Ikeno, Tohru Yamada

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27 Citations (Scopus)

Abstract

The effect of blocking groups and stereochemistry of the substituents on the regio- and stereoselectivity in intramolecular nitrone-alkene cycloaddition (INAC) of hept-6-enoses are reported. L-ribo-Hept-6-enose 12 and D-lyxo-hept-6-enose 15, both containing a 2,3-O-isopropylidene blocking group, and L-xylo-hept-6-enose 23 and D-arabino-hept-6-enose 30, both with a 2,3-O-trans-diacetal blocking group, were prepared from D-ribose and D-arabinose, respectively. With N-alkyl hydroxylamine, lactols 12 and 15 underwent an INAC reaction to give cis-fused isoxazolidines exclusively whereas lactols 23 and 30 gave a mixture of cis-, trans-fused isoxazolidines (cyclohexanols) and bridged isoxazolidines (cycloheptanols). With the 2,3-O-trans-diacetal protecting group, the bridged bicyclo[4.2.1]isoxazolidines (cycloheptanols), via the endo mode of INAC cyclization, were synthesized for the first time from unbranched sugar derivatives 23 and 30. The stereochemical outcomes of these reactions were rationalized on the basis of transition state energies obtained by computation. The present INAC showed trivial temperature, but significant solvent dependence. For lactols 23 and 30, performing the INAC in 2-propanol gave the best yields of fused isoxazolidines (cyclohexanols) whereas in dichloromethane afforded the best yields of bridged isoxazolidines (cycloheptanols).

Original languageEnglish
Pages (from-to)3253-3263
Number of pages11
JournalJournal of Organic Chemistry
Volume71
Issue number8
DOIs
Publication statusPublished - 2006 Apr 14

ASJC Scopus subject areas

  • Organic Chemistry

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