= Solution
<methyl fluorosulfonate> alkylates the tertiary <isoxazolidine> <nitrogen>, giving a \b[quaternary N-methyl ammonium salt]; the methyl remains attached to <nitrogen> in F. <hydride> from <lithium aluminium hydride> then cleaves the N–O bond, releasing the corresponding <oxygen> as an aluminium-bound <alkoxide> while restoring neutral <tertiary amine> <nitrogen>. Aqueous workup protonates the <alkoxide> to give the <alcohol>.
Thus the C–O bond made in the <cycloaddition> survives as the alcohol-bearing C–O bond, and the formaldehyde-derived methylene survives as the extra <carbon> between <nitrogen> and the <carbon> framework. The N–O bond is the one removed. \b[N-methylation followed by reductive N–O cleavage gives the bridged amino <alcohol> F] without requiring cleavage of its newly formed C–C bond or hydrogenation of a nonexistent residual <alkene>.
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