From 1,3-cyclohexadiene through nitrosocarbonyl chemistry, the synthesis of pyrimidine isoxazoline-carbocyclic nucleosides

N-Benzoyl-2-oxa-3-azabicyclo[2.2.2]oct-5-ene undergoes cycloaddition with benzonitrile oxide affording a mixture of syn and anti regioisomeric cycloadducts. The anti cycloadducts were easily elaborated to stereodefined isoxazoline-carbocyclic aminols that served as synthons for the linear construction of pyrimidine nucleosides, while the syn cycloadducts do not enter the same synthetic route.