be prepared in high yields at high purities by this process application_number US 13604187 A description the process according to the present invention is illustrated by the following reaction scheme str4 wherein x represents a halogen atom the reaction between monomethyl succinate 5 and an alkyl chlorocarbonate is carried out in an organic solvent in the presence of a base the alkyl chlorocarbonate which can be used in this reaction is not particularly limited and usually includes an ethyl ester to advantage the base to be used is not also particularly limited as long as it is capable of scavenging hydrogen chloride produced by the reaction and does not hinder the reaction such a base preferably includes organic bases e g alkylamines e g trimethylamine triethylamine etc pyridine etc the organic solvent to be used preferably but unrestrictedly include hydrocarbons e g benzene toluene hexane and ethers e g diethyl ether tetrahydrofuran the reaction temperature is usually room temperature or lower and preferably 0 u00b0 c or lower the acid anhydride 6 is then reacted with a grignard reagent of 1 decyne the reaction may be effected by adding a grignard reagent of 1 decyne dropwise to the reaction mixture containing the acid anhydride 6 as produced or the latter may be.