prov:value
| - or ethanesulphonyl chloride, or isobutyl chloroformate, in the presence or absence of an inert organic solvent such as a halogenated hydrocarbon, e.g. chloroform or methylene chloride, or an ether, e.g. diethyl ether or tetrahydrofuran, to prepare a mixed acid anhydride of the acid, and adding thereto, at a temperature of 0??? C. to ambient, an alcohol R4 OH, wherein R4 is other than a hydrogen at
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