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The Structural Determination of Drotaverine Hydrochloride Using NMR Studies
Author(s) -
Kuz'mitalya E.,
Moiseev Sergey V.,
Khorolskiy Mikhail D.,
Lutceva Anna I.
Publication year - 2020
Publication title -
chemistryselect
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.437
H-Index - 34
ISSN - 2365-6549
DOI - 10.1002/slct.202001180
Subject(s) - hydrochloride , intramolecular force , tautomer , chemistry , stereochemistry , organic chemistry
In product specification files and scientific literature, the international name of drotaverine hydrochloride is assigned to two different chemical compounds: 1‐(3,4‐diethoxybenzylidene)‐6,7‐diethoxy‐1,2,3,4‐tetrahydroisoquinoline hydrochloride (I) and 1‐(3,4‐diethoxybenzyl)‐6,7‐diethoxy‐3,4‐dihydroisoquinoline hydrochloride (II). These compounds are double bond position isomers; each of them has its own CAS number and the international chemical structural identifier‐InChIKey. The fact that there are two different structural formulas under the name of drotaverine hydrochloride can be explained by the intramolecular tautomerism between the compounds I and II. The aim of the study is to determine the structure of drotaverine hydrochloride samples with different structural formulas using NMR spectroscopy, and explore the possibility of their intramolecular rearrangement. We studied twenty‐two samples of drotaverine hydrochloride produced by various manufacturers. All the studied samples were found to be the compound II. Changes in the temperature, solvent, and pH did not cause the intramolecular tautomerism and conversion of the compound II into the compound I. There is no published evidence of methods, specific for either of the compounds, that confirm the structure of the compound I. The international non‐proprietary name of drotaverine hydrochloride was found to correspond to the compound 1‐(3,4‐diethoxybenzyl)‐6,7‐diethoxy‐3,4‐tetrahydroisoquinoline hydrochloride.