One-pot regioselective synthesis of 2I,3I-O-(o-xylylene)-capped cyclomaltooligosaccharides: tailoring the topology and supramolecular properties of cyclodextrins

Abstract

The alpha,alpha'-dibromo-o-xylylene cap has been installed at the secondary hydroxyls of a single glucopyranosyl residue in cyclodextrins in one pot and with total regioselectivity; the resulting cyclic ether acts as a removable hinge, allowing selective elaboration of the secondary face and modulating both the self-association and the inclusion capabilities of the hosts.

Dynamic Self‐Assembly of Polycationic Clusters Based on Cyclodextrins for pH‐Sensitive DNA Nanocondensation and Delivery by Component Design

“…The hinge-type diether linkage involving a single glucopyranosyl unit prevents self-inclusion of the aromatic ring into the CD cavity as well as supramolecular oligomerization processes. [18] Different from the previously reported paCDs, it favors the formation of well-defined dimeric species with appropriate topology to undergo DNA templation in a dynamic, hierarchical, and reversible manner that is switched onoff at a physiologically relevant pH window ( Figure 2). Compounds 1 and 2, differing in the structure of the cationic heads, and the C 7 -symmetrical analogues 3 [19] and 4, lacking the xylylene moiety, were considered in this work to test the above concept.…”

“…"open" conformational change on going from the monomer to a head-to-head dimer as already observed for neutral CD-xylylene derivatives (Figure 3). [18] In the dimer, the xylylene group would be shielded from bulk water, whereas it would be exposed in the monomer, leading to a decrease in solubility. Although the complexity of the NMR spectra of 2 prevented a similar analysis (note that both 1 and 2 are nonsymmetrical heptasaccharide derivatives), an analogous behavior can be expected.…”

Cyclodextrin-based multivalent glycodisplays: covalent and supramolecular conjugates to assess carbohydrate–protein interactions

“…Differences in the steric accessibility and acidity of the three types of hydroxyls in the molecule have been taken into account to conceive efficient position-selective and face-selective chemical functionalization methodologies. [17][18][19][20][21][22][23][24][25][26][27] A variety of multivalent conjugates with diverse architectures becomes then accessible through appropriate ligation chemistries (Fig. 1).…”

Efficient regioselective O3-monodesilylation by hydrochloric acid in cyclodextrins

“…27e29 a,a-Dibromo-o-xylylene can also be regioselectively introduced to O2 and O3 of one glucose unit of CDs 30,31 to form O2,O3-capped derivatives (28e33% yields), and the o-xylylene can be advantageously removed by hydrogenation. More recently, diisobutylaluminum hydride (DIBAL-H) has been shown to reductively remove either methyl groups from both O2 and O3 positions of per-O-methylated CDs 32 or benzyl groups from per-2,3,6-O-benzylated a-CD; 33 in the latter case, the benzyl groups were removed in a sequential fashion to form 3 A ,6 A ,6 D -tri-O-debenzylated a-CD derivative.…”