NITRILE OXIDES IN MEDICINAL CHEMISTRY-- 2. SYNTHESIS OF THE TWO ENANTIOMERS OF DIHYDROMUSCIMOL

Article abstract of DOI:10.1016/S0040-4020(01)89765-9

The cycloaddition of bromonitrile oxide to monosubstituted olefins has a high regioselectivity yielding 3-bomo-5-substituted isoxazolines contaminated by minor amounts (4-9percent) of the 4-substituted isomer.The adducts of bromonitrile oxide to allyl alcohol and N-protected allylamine were employed as key intermediates in the preparation of racemic dihydromuscimol (DHM).The synthesis of (R)-(-)- and (S)-(+)-DHM was accomplished by using the two diastereomers obtained by the cycloaddition of bromonitrile oxide to (S)-(+)-isopropylidene-3-buten-1,2-diol.The enantiomeric excess of R)-(-)- and (S)-(+)-DHM, determined by capillary GLC on the appropriate precursors, were 98.8 and >99.0 percent.A spectroscopic survey of the tautomerism of 3-hydroxyisoxazolines indicates the predominant or exclusive occurence of the NH form.