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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 17, Number 11
BKCSDE 17(11)
November 20, 1996 

1H NMR Study of the Inclusion Complexes of Chiral Aromatic Guests with β-Cyclodextrin and Its Derivatives: Discrimination of Aromatic Protons and Chiral Recognition
Kwanghee Koh Park*, Jong Mok Park
The effects of β-CD, Me-β-CD, and biphenyl capped β-CD on 1H NMR spectra of mandelic acid 1, α-methylbenzylamine 2 and 2-phenylpropionic acid 3 were investigated. Enantiomeric recognition was observed for mandelic acid 1 by all the hosts used, for α-methylbenzylamine 2 by β-CD and Me-β-CD, and for 2-phenylpropionic acid 3 by Me-β-CD. In the presence of biphenyl-capped β -CD, ο-, m-, and p-protons of the phenyl groups of the guests are discriminated due to ring current of the capped biphenyl group. The splitting pattern of the phenyl protons indicates that the phenyl group of the guests is inserted into the β-CD cavity from the secondary hydroxyl side and positioned in close proximity to the capped biphenyl ring. The magnitude of the upfield shifts of H3 and H5 protons of β-CD upon binding of guests 1-3 is similar to that caused by ephedrine or pseudoephedrine, suggesting that the substitution at benzylic carbon atom has little effect on the depth of the insertion of the phenyl group into the β-CD cavity and stability of the inclusion complexes.
1052 - 1056
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