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Structural Studies of Self‐Folding Cavitands
Author(s) -
Shivanyuk Alexander,
Rissanen Kari,
Körner Steffi K.,
Rudkevich Dmitry M.,
Rebek, Jr. Julius
Publication year - 2000
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/1522-2675(20000809)83:8<1778::aid-hlca1778>3.0.co;2-j
Subject(s) - chemistry , cavitand , resorcinarene , hydrogen bond , amide , crystallography , enantiomer , intramolecular force , folding (dsp implementation) , solvent , foldamer , nuclear magnetic resonance spectroscopy , crystal structure , stereochemistry , molecule , organic chemistry , supramolecular chemistry , engineering , electrical engineering
Resorcinarene‐based cavitands 1a – c fold into a deep open‐ended cavity by means of intramolecular hydrogen bonds in both apolar solutions and the solid state. The X‐ray crystal‐structure analysis of cavitand 1a features a seam of secondary amide C=O⋅⋅⋅H−N interactions that bridge adjacent rings and are held in place by intra‐annular hydrogen bonds. This results in a cavity of 9.2×7.0 Å dimensions. The arrangement of the amides in 1a – 1c is cycloenantiomeric, with clock‐ and counterclockwise orientation of the head‐to‐tail amide sequence. Interconversion rates of the two enantiomers are controlled by solvent polarity: the rate is slow on the NMR time‐scale in aromatic solvents and CDCl 3 , but fast in (D 6 )acetone. The 1 H‐ and 13 C‐NMR‐spectral analysis is in agreement with the crystallographic data. Chiral cavitand 1b with eight HN−C(O)−C*HMeEt ((+)‐( S )) groups on its upper rim exists as two cyclodiastereoisomers (in a ca. 3 : 1 ratio) in apolar solution. A `library' of 512 diastereoisomeric cavitands 1c is obtained as a mixture by using the corresponding racemic acid chloride.