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Crystal Structure of Quinine: The Effects of Vinyl and Methoxy Groups on Molecular Assemblies of Cinchona Alkaloids Cannot Be Ignored
Author(s) -
Hisaki Ichiro,
Hiraishi Eri,
Sasaki Toshiyuki,
Orita Hideo,
Tsuzuki Seiji,
Tohnai Norimitsu,
Miyata Mikiji
Publication year - 2012
Publication title -
chemistry – an asian journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.18
H-Index - 106
eISSN - 1861-471X
pISSN - 1861-4728
DOI - 10.1002/asia.201200566
Subject(s) - cinchona alkaloids , cinchonine , quinine , quinoline , chemistry , cinchonidine , crystal structure , molecule , crystallization , quinidine , stereochemistry , crystal (programming language) , supramolecular chemistry , crystallography , organic chemistry , enantioselective synthesis , catalysis , medicine , malaria , computer science , programming language , immunology , pharmacology , biology
Abstract Quinine, one of Cinchona alkaloids, has been of great interest from medical, synthetic, and supramolecular viewpoints. However, unaccountably, the guest‐free (GF) crystal of quinine containing no solvent or other molecules has not been reported for nearly three decades, although GF crystals of other Cinchona alkaloids, such as quinidine, cinchonidine, and cinchonine, are already known. In this study, we successfully revealed the crystal structure of quinine, which belongs to the P 2 1 space group with the cell parameters of a =6.0587(1), b =19.2492(5), c =22.2824(7) Å, β =92.1646(11)°, and V =2596.83(12) Å 3 . Interestingly, the crystal has three crystallographically independent molecules in the cell ( Z′ =3) that are connected through a N(quinoline)⋅⋅⋅HO hydrogen bond to form a pseudo three‐two‐fold (3 2 ) double‐helical motif. The helical motif is completely different from those observed in GF crystals of other Cinchona alkaloids. Hierarchical comparison on the crystal structures of a series of Cinchona alkaloids including quinine clearly demonstrated that only small structural differences of a molecule, particularly the position of the vinyl group, cause a significant variety of assembly manner in the crystalline state. There have been no reports systematically demonstrating such steric effect in crystals of Cinchona alkaloids, and, therefore, the present system contributes to the design of desired functional crystal structures.