D_3h‐Symmetrical Shape‐Persistent Macrocycles Consisting of Pyridine–Acetylene–Phenol Conjugates as an Efficient Host Architecture for Saccharide Recognition

Abstract

Hexagonal shape-persistent macrocycles (SPMs) consisting of three pyridine and three phenol rings linked with acetylene bonds were developed as a preorganized host for saccharide recognition by push-pull-type hydrogen bonding. Three tert-butyl or 2,4,6-triisopropylphenyl substituents were introduced on the host to suppress self-aggregation by steric hindrance. In spite of the simple architecture, association constants K of the host with alkyl glycoside guests reached the order of 10 m on the basis of UV/Vis titration experiments. This glycoside recognition was much stronger than that in the cases of acyclic equivalent hosts because of the entropic advantage brought by preorganization of the hydrogen-bonding sites. Solid-liquid extraction and liquid-liquid transport through a liquid membrane were demonstrated by using native saccharides, and much preference to mannose was observed.

Metathesis‐Based Stapling of a Pyridine–Acetylene–Phenol Oligomer Having Alkenyl Side Chains after Intermolecular Templation by Native Saccharides

“…As in our preceding reports,, commercially available 2,6‐dibromopyridine and 4‐pentylphenol were used as starting materials for the preparation of the tetraalkenyl substrate 3 (Scheme ). Monomeric intermediates 4‐(3‐butenyloxy)‐2,6‐diiodopyridine ( 5 ), 1,3‐diethynyl‐2‐(methoxymethoxy)‐5‐pentylbenzene ( 6 ),[9a] and trimeric diethynyl intermediate 7 were prepared according to the procedures we reported. The Sonogashira reaction using 6 with an excess amount of 5 gave trimeric diiodo intermediate 8 .…”

“…As the cases of 2 and 3 mentioned above, we examined the solid–liquid extraction ability, for native hexoses for stapled 4 . Powdery d ‐glucose (9 mg) was added to a solution of 4 (1.0 × 10 –5 m ) in DCE (1.0 mL) and shaken for 12 h at room temperature, and then the mixture was diluted to 5.0 mL with DCE.…”

“…THF was freshly distilled from sodium benzophenone ketyl before use. Synthetic intermediates 5 , 6 ,[9a] and 7 were prepared according to the procedure that we previously reported.…”

π‐Conjugated Macrocycles Bearing Angle‐Strained Alkynes

“…Other macrocycles, including alkyne and pyridine moieties, were reported by Baxter,S chlüter,A be and Inouye, and other groups. [205][206][207][208][209][210][211][212][213][214][215][216][217] Bipyridine and terpyridine spacers are also utilized, but thesemacrocyclesare all strain free. Strained macrocycleswith furylene and diethynylfuranmoieties are rare.…”

Saccharide Recognition and Helix Formation in Water with an Amphiphilic Pyridine–Phenol Alternating Oligomer

“…Very recently, we introduced a new type of helical hosts, pyridine–phenol alternating oligomers (Figure b) . These oligomers could interact with saccharides by hydrogen bonding in a push–pull fashion, for which the nitrogen atoms of the pyridine rings and the hydroxy groups of the phenol rings worked as hydrogen‐bonding acceptors and donors, respectively (Figure c) . The oligomers showed extremely high affinity for saccharides in less‐polar solvents and extracted native saccharides into the solvents from solid phases and even from water solutions.…”