Chemistry of synthetic receptors and functional group arrays. 18. Approaches to quantitative supramolecular chemistry. Hydrogen-bond-based molecular recognition phenomena and sigmoidal behavior in multicomponent mixtures

Abstract

m), 980 (w), 905 (w), 860 (w), 830 (w) cm-I; HRMS calcd for CZ4-H,,N305 (M + H) 444.251, found 444.247. Compound 22 can be obtained from 20b by using same procedure, and all the physical and spectral data are identical. Cyclo[N-[ 3-[4 (2-(Z )-aminoviny I) phenoxy) (2S,3S)-prolyl]-( S ) -isoleucyl] (23). To a solution of compound 22 (0.0580 g, 0.139 mmol) andthioanisole (0.173 g. 1.39 mmol) in methylene chloride (3 mL) at 5 'C was added trifluoroacetic acid (TFA) (0.316 g, 2.78 mmol). After 5 h, the reaction was diluted with methylene chloride (10 mL) and made basic with a saturated sodium bicarbonate solution (20 mL). The organic layer was separated and extracted with a 5% citric acid solution (2 mL, twice), and the aqueous layers were combined. The aqueous layer was made basic with a saturated NaHCO, solution, extracted with methylene chloride (20 mL, five times), dried over Na2S04, and filtered, and the filtrate was concentrated under reduced pressure to provide pure 23 (0.0130 g, 28% yield): R~0.52 (methylene chloride:ethanol90:10); [a]"D J = 6.9), 0.84-0.90 (3 H, m), 0.91-0.98 (1 H, m), 1.21-1.33 (1 H, m), 2.07-2.13 (1 H, m), 2.17-2.18 (2 H, m), 2.35-2.43 (1 H, m), 3.04-3.09 (1 H, m), 3.23-3.24 (2 H, m), 4.22-4.25 (1 H, m), 5.18-5.22 (1 H, m), 5.55 (1 H, d, J = 9.

Binding Constants and Their Measurement

“…We now first consider the situation where the guest is "silent", that is, Y G = 0-for instance in UV-vis titrations with a simple noncolored monoatomic ion such as chloride (16).…”

“…As this is only going to be likely in cases where the physical property is concentration dependent (e.g., UV-vis spectroscopy), we start again from (10) using the same approach as with (16) to obtain (23).…”

Recent Developments in Synthetic Chemistry, Chiral Separations, and Applications of Tröger's Base Analogues

“…For instance, various functional groups capable of H-bond formation were installed at the extremities of the V-shaped skeleton of Trçgers base to create synthetic receptors for the recognition of adenine derivatives [6] or dicarboxylic acids [7]. Water-soluble cyclophane-like analogues of Trçgers base have been suggested as chiral receptors for small, neutral organic molecules [8].…”

Rapid Screening of Binding Constants by Calibrated Competitive 1H NMR Spectroscopy

“…This allows us to express [S] free in terms of known values by using Equation (10). The other terms in Equation (9) can also be expressed as known quantities as shown in Equations (11) and (12). This enables a relationship between [R ref .S] (as determined from the change in NMR shift by using the calibration curve) and log K unk to be determined, and hence unknown binding constants can be simply calculated.…”

“…A mixture of reference and unknown receptor was then used to compete for the substrate, and the observed NMR shifts of both receptors allowed the calculation of a binding constant for the ™unknown∫ receptor ± substrate complex. [12] Similar competi-tion experiments have also been used in cases in which complexation is slow on the NMR timescale. [13] Recently, competition experiments in combination with relaxation parameters have been used to develop a high-throughput approach to NMR-based screening.…”