New homologues of chiral cyclohexylhemicucurbit[n]urils

Abstract

The existence of new 7-, 8-, 9-and 10-membered homologues of chiral cyclohexylhemicucurbituril is reported. The barrelshaped (all-R)-cyclohexylhemicucurbit[8]uril ((all-R)-cycHC[8]) was isolated and its complexes with anions were detected in negative ion mode MS. Here, 7-, 9-and 10-membered homologues were detected by HPLC -HRMS. Geometries of all reported macrocycles were calculated using quantum chemical methods, which showed that even-numbered homologues were barrel-shaped and odd-numbered homologues were asymmetrical barrel-shaped with unequal dimensions of the openings. The size of the ((all-R)-cycHC[8]) cavity was comparable to CB[8] and it probably can serve as a chiral host.

Formation and trapping of the thermodynamically unfavoured inverted-hemicucurbit[6]uril

“…Such a single monomer modification and formation of diastereomeric macrocycles lead to the enrichment of the pool of hosts, which is important for the development of highly selective host-guests interactions. In the course of our investigation on the synthesis and binding properties of chiral cyclohexanohemicucurbiturils 30,34,36,44,49,50 (cycHCs), we repeated the synthesis of the previously known achiral cis-cycHC 33 2 (Figure 1). To our surprise, heating cis-N,N-cyclohexa-1,2-diylurea 3 and paraformaldehyde in 4 M HCl gave a new six-membered cycHC 1 (Figure 1) along with the expected 2 in nearly equal quantities ( Figure 2, Scheme 1).…”

Hemicucurbit[n]urils and Their Derivatives – Synthesis and Applications

“…Gas phase calculationson on the (all-S)-cychmCB [6] indicated that the anions were located inside the cavity and the affinity of the anions (in gas phase) is Cl À > Br À > HCOO À > I À . [28] The existence of even larger macrocycles of cyclohexylhemicucurbit[n]uril (n = 7-10) were first shown in 2014 by analysing the reaction mixture of (all-R)-cychmCB [6] by HPLC-MS. [29] The (all-R)-cyclohexylhemicucurbit [8]uril (all-R-cychmCB [8]) was isolated in 11 % yield. The chloride and formate complexes of (all-R)-cychmCB [8] were detected in negativemode MS.…”

Templating Effects in the Dynamic Chemistry of Cucurbiturils and Hemicucurbiturils

“…The diastereomers of the latter, the (S,S)-or (R,R)-cycHC [n] [15,72,74,84] are ball shaped hosts, contrasting to the cylindrical or bamboo stem shapes of the (R,S)-isomers. The cyclohexano groups on each side of the cycHC[n] lean together, creating a round cavity bordered by narrow portals.…”