合成路线1

Condensation of 4-methylacetophenone (I) with ethyl diethoxyacetate (II) in the presence of lithium hexamethyldisilazide afforded diketoacetal (III). Formation of pyrazole (V) was accomplished by treatment of (III) with 4-methoxy-phenylhydrazine (IV). Subsequent acid hydrolysis of the diethyl acetal gave aldehyde (VI), which was condensed with carbon tetrabromide using triphenyl phosphine to furnish dibromoethylene compound (VII). Elimination of HBr in (VII) by treatment with tetrabutylammonium fluoride produced bromo-acetylene (VIII). After lithium-bromine exchange, addition of paraformaldehyde yielded the propargyl alcohol (IX). Further Mitsunobu coupling of (IX) with N,O-bis(phenoxycarbonyl)hydroxylamine (X) gave the N,O-bis-protected N-alkyl hydroxylamine (XI). This was finally converted to the title N-hydroxyurea by treatment with methanolic ammonia.