Abstract: A method of producing an N-demethyl-N-isopropyl-8,9-anhydroerythromycin A-6,9-hemiacetal or a salt thereof, characterized in that an N-demethylerythromycin A or a salt thereof is reacted with an isopropylating agent and subsequently treated under acidic conditions, and a method of producing a substantially pure crystal of an 8,9-anhydroerythromycin A-6,9-hemiacetal derivative represented formula (VI): ##STR1## wherein R.sup.1 and R.sup.2, whether identical or not, represent an alkyl having 1 to 6 carbon atoms, an alkenyl having 2 to 6 carbon atoms or an alkynyl having 2 to 6 carbon atoms; R.sup.3 represents hydrogen or a hydroxyl group; one of R.sup.4 and R.sup.5 represents hydrogen and the other represents a hydroxyl group, or R.sup.4 and R.sup.5 bind together to represent O.dbd.; R.sup.6 represents hydrogen or a hydroxyl group that may be substituted for; R.sup.

Abstract: A compound of the formula:A--CH.sub.2 CH.sub.2 --O--B[wherein A stands for an aromatic ring residue, a group shown by R.sup.1 --CO-- (wherein R.sup.1 stands for an aliphatic hydrocarbon residue, aromatic hydrocarbon residue, a heterocyclic residue, an aromatic alipahtic hydrocarbon residue or an alicyclic hydrocarbon residue) or R.sup.2 --CH.dbd.CH-- (wherein R.sup.2 stands for an aliphatic hydrocarbon residue an aromatic hydrocarbon residue a heterocyclic residue an aromatic aliphatic hydrocarbon residue or an alicyclic hydrocarbon residue), and B stands for an aromatic ring residue], can be obtained in high yield, at high purity level by short reaction time, by reacting a compound of the formula:A--CH.sub.2 CH.sub.2 --X(wherein A is of the same meaning as defined above, and X stands for a leaving group) with a compound represented by the general formula:MO--B(wherein M stands for an alkali metal atom or an alkaline earth metal atom and B is of the same meaning as defined above) in a non-aqueous solvent.

Abstract: A method of producing diethanolamine derivatives or acid salts thereof according to the reaction scheme: ##STR1## wherein X stands for a leaving group; and R.sup.1 stands for an alkylcarbamoyl group, which provides an industrially advantageous method of preparing the subject matter useful as an antiarrhythmic agent.