SummaryCommercial methyl hydrogen nonandioate is of unsatisfactory quality for the preparation of queen honeybee methyl ester, methyl 9-oxodec-2-enoate. We give practical details for the synthesis from commercial nonandioic acid of half ester-acid chloride of high quality; this is converted to methyl 9-oxodecanoate using methyl aluminium dichloride. Queen bee ester was prepared from the ester enolate of methyl 9-oxodecanoateviamethyl 9-oxo-2-phenylselenodecanoate. Details are given for careful purification at crucial stages, and the mass spectra and other spectra of a number of pure compounds are recorded.