Precision studies in supramolecular chemistry: a ¹H NMR study of hydroxymethoxyacetophenone/β‐cyclodextrin complexes

Abstract

The association constants for the interactions of 2-hydroxy-4-methoxyacetophenone, 2-hydroxy-5-methoxyacetophenone, 2-hydroxy-6-methoxyacetophenone, 3-hydroxy-4-methoxyacetophenone and 4-hydroxy-3-methoxyacetophenone with β-cyclodextrin in water were measured by (1)H NMR and by isothermal titration calorimetry. Very good agreement was obtained between the different methods. The errors associated with the NMR method for measuring mM binding affinities were estimated to be 10-30%, and by isothermal titration calorimetry, 10-20%. Rotating frame nuclear Overhauser effect spectroscopy studies show that the solution phase host-guest complexes formed by β-cyclodextrin with these hydroxymethoxyacetophenone derivatives are not structurally well defined but that the hydroxymethoxyacetophenone derivatives are mostly associated with the narrow primary hydroxyl rim.

Bioassay-directed isolation of falcarindiol and isoacetovanillon from Pycnocycla caespitosa based on KCl-induced contraction in rat uterus smooth muscles

“…1 H-NMR spectrum showed ABX spin pattern similar to trisubstituted vanillin derivatives at δ H 7.47 (1H, d, J = 2.0 Hz, H-2), 7.47 (1H, dd, J = 8.7, 2.0 Hz, H-6), 6.88 (1H, d, J = 8.7 Hz, H-5), one methoxy at δ H 3.89 (3H, s), and one downfield methyl singlet at δ H 2.49 (3H, s). These data were similar to those reported for isoacetovanillone which was more confirmed by co-TLC with standard ( 19 ).…”

Tuning temperature responsive poly(2-alkyl-2-oxazoline)s by supramolecular host–guest interactions

“…This is in agreement with the evolution of any observable shift due to a supramolecular association, leading to a plateau value at full complexation. 34,35 It thus seems that the fully complexed copolymer-αCD ensemble exhibits a phase transition around 40 °C. When considering the length of a fully stretched nonyl alkylic chain, of ca.…”

Phytochemical Profile of the Aerial Parts of Sedum sediforme and Anti-inflammatory Activity of Myricitrin

“…gradient fast centrifugal partition chromatography (FCPC) ® , silica gel and Sephadex ® column chromatography (CC), as well as preparative thin layer chromatography. Twenty-six compounds were identified as phlorin (1) [9], picraquassioside D (2) [4], protocatechuic acid (3) [10], phloroglucin-1-O-(6''-galloyl-glucoside) (4) [11], gallincin (5) [12], aesculetin (6) [13], caffeic acid (7) [10], piceol (8) [14], syringic acid ( 9) [15], eriodictyol-4',7-O-diglucoside (10) [16], apocynin (11) [17], eriodictyol-4'-O-glucoside ( 12) [18], myricitrin (13) [19], eriodictyol ( 14) [13], quercitrin (15) [20], myricetin-3-O-(2''galloylrhamnoside) ( 16) [21], myricetin-3-O-(3''-galloyl-rhamnoside) (17) [21], naringenin (18) [22], (2R * , 3R * )-5,7-dihydroxy-2,3-dimethyl-4-chromanone ( 19) [23], quercetin (20) [24], luteolin (21) [24], taraxeryl acetate ( 22) [25], lupeol (23) [26], germanicyl formate (24) [27], ß-sitosterol (25) [10], and ß-sitosterol Compound 27 was identified as the 7-O-ß-D-glucoside of (2R * , 3R * )-5,7-dihydroxy-2,3-dimethyl-4-chromanone, an aglycone which was previously described by Mutanyatta-Comar et al [23]. The 1 H NMR spectrum showed two doublets at δ H 1.19 (3H, J = 7.0 Hz) and δ H 1.48 (3H, J = 6.3 Hz) representing two methyl groups bonded to the sp 3 Also the structure of the new alkyl glycoside 28 was elucidated by means of 1D-and 2D-NMR spectroscopy.…”