A quantitative method for analysis of mixtures of homologues and stereoisomers of hemicucurbiturils that allows us to follow their formation and stability

Abstract

Cyclic and linear oligomers of hemicucurbiturils have large difference in UV absorbance.

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

“…Aav and co-workers very recently published a HPLC-UV procedure to quantitatively assess the distribution of products in the reaction mixture of (R,S)-and (all-R)-cychmCB[n]s. [32] In contrast to biotinuril results from Pittelkow, [5] they found that the value of the molar extinction coefficient of the absorption at 210 nm showed no trends with respect to amount of monomeric units in macrocycles or oligomers. In fact, macrocyclic species seemed to possess absorptivities an order of magnitude higher than the oligomers, which was attributed to fewer degrees of freedom in the macrocycles.…”

Templating Effects in the Dynamic Chemistry of Cucurbiturils and Hemicucurbiturils

“…General scheme of dynamic formation of CB macrocycles. [50] We speculate that it is due to higher conformational flexibility of these compounds compared to their cyclic analogues. A) Crystal structure of C-shaped 6-membered glycoluril oligomer [40] (CCDC 701740); B) C-shaped dimer of glycoluril with aromatic terminal groups; S-shaped dimer of glycoluril with aromatic terminal groups.…”

“…Though, Scheme 4. [15,50] Also, surprisingly, a very large discrepancy in the UV absorbance between linear and macrocyclic congeners of cycHCs was observed (Table 1). Figure 2.…”

“…Map of electronic potential of CB [7] and the methylsubstituted bambus [6]uril (MeBU [6]) is shown on Figure 4. [50] Compound e 210 (M À1 cm À1 ) 6-membered oligomer (2 AE 1) · 10 3 (R,S)-cycHC [6] (18.4 AE 0.2) · 10 3 (R,R)-cycHC [6] (17 AE 2) · 10 3 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 Electron rich oxygens of urea monomers surround the opening of the CB cavity, through which electron poor cationic species bind to CBs. UV absorption of linear oligomer and macrocycles formed from cyclohexanediylurea.…”

Size-Control by Anion Templating in Mechanochemical Synthesis of Hemicucurbiturils in the Solid State

“…Due to the different elution conditions between the HPLC and HPLC-MS systems, the compound retention times on the obtained HPLC chromatograms were not equal, which is why we refrained from assigning MS data to specific peaks on the shown HPLC chromatograms, except for the previously identified cycHC[6] and cycHC [8] (ref [5]). Figure S31.…”