An Improved Synthesis of 6-Deoxy-Analogues of Cyclodextrins and Amylose. Further Interpretations of the Proton Magnetic Resonance Spectra of the Peracetates of Cyclodextrins and Amylose

Unnatural cyclodextrins can be accessed from enzyme-mediated dynamic combinatorial libraries

Dynamic systems of cyclodextrins (CDs) enabled by a native cyclodextrin glucanotransferase (CGTase) can incorporate unnatural glucopyranose-derived building blocks, expanding the applicability of enzyme-mediated dynamic combinatorial chemistry by using synthetically modified substrates. Starting dynamic combinatorial libraries from CDs with a single 6-modified glucopyranose results in a dynamic mixture of CDs containing several modified glucopyranoses. The relative concentrations of modified α, β or γ-CDs can be controlled by the addition of templates, providing a novel way to access modified CDs.

The uncommon strong inhibition of α-glucosidase by multivalent glycoclusters based on cyclodextrin scaffolds

New inhibitors of α-glucosidase based on perglycosylated cyclodextrins were synthesized via click-chemistry and compared to acarbose.

Synthesis of mono-6-deoxy-6-N,N,N′,N′,N′-pentamethylethylenediammonio-cyclomaltoheptaose, a single-isomer, monosubstituted, permanently dicationicβ-CD and its use for enantiomer separations by CE

The dichloride salt of mono-6-deoxy-6-N,N,N',N',N'-pentamethylethylenediammonio-cyclomaltoheptaose (PEMEDA-BCD), the first single-isomer, monosubstituted, permanently dicationic beta-CD has been synthesized, analytically characterized, and used for the capillary electrophoretic separation of the enantiomers of a group of analytes in acidic and basic BGEs. When the concentration of PEMEDA-BCD was changed in the BGEs, the resulting effective mobilities of the analytes and the respective separation selectivities followed the predictions of the ionic strength-corrected charged resolving agent migration model. Good separation selectivities and favorable normalized EOF mobilities allowed for the rapid, efficient separation of the enantiomers of anionic, weak acid and nonionic analytes in the low- and/or high-pH BGEs.

Per(6-guanidino-6-deoxy)cyclodextrins: synthesis, characterisation and binding behaviour toward selected small molecules and DNA

Per(6-guanidino-6-deoxy)-cyclodextrins , and are novel derivatives, resulting from homogeneous introduction of the guanidino group at the primary side of alpha-, beta- and gamma-cyclodextrins. The products were obtained from the corresponding amino derivatives, as direct guanidinylation of the known bromo-cyclodextrins provided mixtures. The new compounds were fully characterized by NMR spectroscopy and other analytical methods, and their interaction with guest molecules was studied. Strong complexation with 4-nitrophenyl phosphate () disodium salt was observed (K(binding) approximately 5 x 10(4) M(-1)), whereas the non-phosphorylated substrate nitrobenzene () formed a very weak complex. 2D ROESY spectra revealed cavity inclusion in both cases, however the orientation of was opposite to that of , such that the phosphate group is oriented toward the primary side facing the guanidine groups. The strong affinity of towards the phosphorylated guest suggested that interaction with DNA was possible. The new compounds were found to completely inhibit the migration of ultra pure calf thymus DNA during agarose gel electrophoresis, whereas no effects were observed with guanidine alone or with the plain cyclodextrins. Further, the condensation of DNA into nanoparticles in the presence of was demonstrated by atomic force microscopy, confirming strong electrostatic interaction between the biopolymer and the multicationic products . The strong guanidine-phosphate interactions between and DNA were therefore attributed to the clustering of the guanidine groups in the primary area of the cyclodextrin. Cavity effects could not be assessed.

Synthesis of 2-deoxy-alpha-D-arabino-hexopyranosyl phosphate and 2-deoxy-maltooligosaccharides with phosphorylase

A convenient one-step synthesis of 2-deoxy-alpha-D-arabino-hexopyranosyl phosphate on a millimolar scale is described by reaction of potato phosphorylase with D-glucal at equimolar phosphate concentration. Furthermore, in the presence of catalytic amounts of phosphate, a 2-deoxy-maltooligosaccharide is obtained from maltotetraose and D-glucal. The water-insoluble oligosaccharide was isolated and characterized by 1H and 13C NMR spectroscopy. An average dp of 20 was thus determined.

Selective pivaloylation and diphenylacetylation of cyclomalto-oligosaccharides

Regioselective acylation of cyclomalto-oligosaccharides was achieved using pivaloyl and diphenylacetyl chlorides. The reaction of cyclomaltohexaose (1) with pivaloyl chloride gave the hexakis(2,6-di-O-pivaloyl) derivative 19 in 66% yield. Similar reaction with cyclomalto-heptaose (2) led to the octakis(2I,6I,6II,6III,6IV,6V,6VI ,6VII-O-pivaloyl) 26 and the 17 heptakis(6-O-pivaloyl) derivatives in 34 and 26% yields, respectively. The octakis(6-O-pivaloyl) derivative 18 was the only compound isolated (72%) in the reaction of pivaloyl chloride with cyclomalto-octaose (3). Diphenylacetylation of 1-3 gave the symmetrical (20-22) and the non-symmetrical (27-29) per(6-O-diphenylacetyl) esters as major and minor products, respectively.

Synthesis of 6-deoxymaltooligosaccharides and a study of their lipid-binding properties

Amylose reacted in N,N-dimethylformamide with crystalline bromomethylenedimethylammonium bromide (Vilsmeier bromide) to give 6-bromo-6-deoxyamylose with a high degree of substitution. Reduction of the bromoamylose with sodium borohydride yielded 6-deoxyamylose that, following controlled acetolysis, gave 6-deoxymaltooligosaccharides. Such oligosaccharides, of appropriate chain-length, formed stable complexes with long-chain fatty acids that have a dissociation constant of about 2 microM in their interaction with parinaric acid (trans-9,11,13,15-octadecatetraenoic acid). Treatment of 6-bromoamylose with sodium methoxide in dimethyl sulfoxide produced a 3,6-anhydroamylose that contains few unaltered D-glucose units. This anhydroamylose also bound to a palmitoyl-resin column, suggesting that the polymer may be partially helical and somewhat lipophylic. Finally, reaction of 6-bromoamylose with methylvinyl ether led to the 2,3-di(methoxyethyl) ether that, on reaction with sodium methoxide, gave the 6-methyl ether from which 6-O-methylamylose was obtained by mild acid hydrolysis.

Enzymic degradation of the mycobacterial O-methyl-D-glucose polysaccharide by a Rhizopus-mold alpha amylase, an enzyme active on 6-O-methyl-amylo-oligosaccharides

An enzyme activity that catalyzes hydrolysis of an alpha-(1----4)-linked 6-O-methyl-D-glucan was detected in, and purified from, Rhizopus oryzae mold. The enzyme acts like an alpha amylase and digests unmodified amylo-oligosaccharides 10 to 15 times as fast as it does the 6-O-methyl and 6-deoxy derivatives. When the limit product obtained by digesting the mycobacterial O-methyl-D-glucose polysaccharide with pancreatic alpha amylase and Aspergillus glucoamylase was further digested with the Rhizopus alpha amylase, di-, tri-, and tetra-saccharide fragments composed of alpha-(1----4)-linked 6-O-methyl-D-glucose were released. The rest of the molecule was recovered as oligosaccharides terminated by two, or three, alpha-(1----4)-linked 6-O-methyl-D-glucose residues.

Hexadeoxycycloheptaamylose-pyridoxamine, an artificial transaminase with a "deeper" binding pocket

Cycloheptaamylose was converted in four steps into a monosulfonylated, hexadeoxy derivative that, on treatment with pyridoxaminethiol, provided an artificial transaminase with activity similar to that found in the nondeoxygenated analogue. Characterization of the intermediate hexadeoxycycloheptaamylose was facilitated by the use of field-desorption mass spectrometry, which was uniquely able to distinguish between penta-, hexa-, and hepta-deoxycycloheptaamylose. A detailed description of experimental methods for the first time makes this modified binding-site available for general use in the design of enzyme mimics.