Molecular recognition of N-acetyltryptophan enantiomers by β-cyclodextrin

Autor: Spyros D. Chatziefthimiou, Mario Inclán, Petros Giastas, Athanasios Papakyriakou, Konstantina Yannakopoulou, Irene M. Mavridis
Jazyk: angličtina
Rok vydání: 2017
Předmět:
Zdroj: Beilstein Journal of Organic Chemistry, Vol 13, Iss 1, Pp 1572-1582 (2017)
Druh dokumentu: article
ISSN: 1860-5397
DOI: 10.3762/bjoc.13.157
Popis: The enantioselectivity of β-cyclodextrin (β-CD) towards L- and D-N-acetyltryptophan (NAcTrp) has been studied in aqueous solution and the crystalline state. NMR studies in solution show that β-CD forms complexes of very similar but not identical geometry with both L- and D-NAcTrp and exhibits stronger binding with L-NAcTrp. In the crystalline state, only β-CD–L-NAcTrp crystallizes readily from aqueous solutions as a dimeric complex (two hosts enclosing two guest molecules). In contrast, crystals of the complex β-CD–D-NAcTrp were never obtained, although numerous conditions were tried. In aqueous solution, the orientation of the guest in both complexes is different than in the β-CD–L-NAcTrp complex in the crystal. Overall, the study shows that subtle differences observed between the β-CD–L,D-NAcTrp complexes in aqueous solution are magnified at the onset of crystallization, as a consequence of accumulation of many soft host–guest interactions and of the imposed crystallographic order, thus resulting in very dissimilar propensity of each enantiomer to produce crystals with β-CD.
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