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 regioisorneric cycloadducts. The anti cycloadclucts were easily elaborated to stereodefined isoxazoline-carbocyclic arninols that served as synthons for the linear construction of pyrimidine nucleosides, while the syn cycloadclucts do not enter the same synthetic route.