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Crystal structures of racemic and enantiopure synephrine correlated with physicochemical properties from IR spectroscopy and thermal analysis
Author(s) -
Fujii Isao
Publication year - 2018
Publication title -
acta crystallographica section c
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.304
H-Index - 17
ISSN - 2053-2296
DOI - 10.1107/s2053229618014419
Subject(s) - enantiopure drug , chemistry , zwitterion , enantiomer , molecule , deprotonation , hydrogen bond , stereochemistry , crystal structure , crystallography , tautomer , ring (chemistry) , conformational isomerism , infrared spectroscopy , organic chemistry , enantioselective synthesis , ion , catalysis
The proto‐alkaloid synephrine {SYN; systematic name: 4‐[1‐hydroxy‐2‐(methylamino)ethyl]phenol}, C 9 H 13 NO 2 , is found to crystallize as a neutral molecule in the racemate and as a zwitterion in the pure enantiomer, in which the phenolic H atom has been transferred to the amino group. In the racemate crystal, an enantiomeric pair on an inversion centre is weakly linked by alcoholic O—H and N—H groups into an R 2 2 (10) ring. The trigonal pyramidal amino group is also linked to the phenolic and alcoholic groups to form a C (6) chain. In the enantiopure crystal, the deprotonated phenolic O atom is involved in trifurcated hydrogen bonding to two quaternary ammonium groups and an alcoholic O—H group to form a fused R 2 4 (11) ring and a C (7) chain. From the results of the crystal structure analysis, thermal analyses and DFT calculations validated from FT–IR spectra, a different tautomer was found in the racemic molecule (RS‐SYN) versus the enantiopure molecule (R‐SYN).