The reductive cyclization of dimethyl 4-nitropimelate (I) with H2 over Pd/C in methanol gives 3-(2-oxo-5-pyrrolidinyl)propanoic acid (II), which is then treated with hot acetic anhydride.
Dexanabinol (I) was brominated using carbon tetrabromide in the presence of triphenylphosphine. The resultant allylic bromide (II) was then condensed with the lithium salt of imidazole (III) to produce the title compound.