Synthesis of the precursors of iminosugars with 7-membered ring.

d-Glucose was converted into the orthogonally protected open-chain derivative having different blocks at both terminal positions: C1 and C6. Selective deprotection of the C1-position opened a route to intermediate with the D-gluco-configuration, while deprotection at the C6-position gave the L-gulo isomer. In both derivatives, the oxime functionality was installed at the proper terminal position, which produced the corresponding precursors of a family of 7-membered ring iminosugars. One of these oximes was converted into the direct precursor: 6,1-bromonitrile.

Fluorescent Molecular Cages with Sucrose and Cyclotriveratrylene Units for the Selective Recognition of Choline and Acetylcholine.

The synthesis of four fluorescent diastereoisomeric molecular cages containing cyclotriveratrylene and sucrose moieties connected via the naphthalene linkers is reported. These diastereoisomers were found to be selective and efficient receptors for acetylcholine and choline. Compound P-5a has a better affinity for choline over acetylcholine, while cage M-5a exhibits a higher association constant for acetylcholine over choline. The highest selectivity value was observed for compound M-5a (KACh/KCh = 3.1). Cages P-5a, P-5b, M-5a, and M-5b were fully characterized by the advanced NMR techniques, and ECD spectroscopy was supported by DFT calculations. The binding constants Ka of these receptors were determined by fluorescence titration experiments in acetonitrile.

Visible-Light Responsive Sucrose-Containing Macrocyclic Host for Cations.

Chiral photoresponsive host 1 was prepared by a high-yield Cs2CO3-templated macrocyclization. Trans-1 transforms into long-lived cis-1 (25 days) upon irradiation with green light, and the backward transformation is triggered by blue light. Both isomers prefer potassium among alkali metal cations, and cis-1 binds cations stronger than trans-1 (Kcis/Ktrans ≤ 4.1). 1H NMR titration experiments as well as density functional theory studies reveal that sucrose ring oxygen residues and azobenzene nitrogen atoms in 1 contribute to cation coordination.

Synthesis of Highly Oxygenated Bicyclic Carbasugars. Remarkable Difference in the Reactivity of the d-gluco and d-xylo- Derived Trienes.

2,3,4-Tri-O-benzyl-D-xylopyranose was used as a starting material in the preparation of the corresponding triene, which underwent smooth cyclization to a polyhydroxylated hydrindane, as a single diastereoisomer. The analogous triene prepared from D-glucose did not undergo any cyclization even under high pressure.

Stereocontrolled Debenzylative Cycloetherification Reaction as a Route to Enantiopure C-Furanosides with Amino Substituents in the Side Chain.

A highly efficient methodology of the preparation of synthetically important tetrahydrofuran derivatives with an amino substituent in the side chain is reported. This process is based on the stereocontrolled debenzylative cycloetherification (DBCE) reaction applied for chirons from the d-gluco- and d-manno-series and provides derivatives with new stereogenic centers. The influence of the electron-withdrawing group (EWG), present in the acyclic substrates with the mesyl leaving group, on the reactivity in the DBCE reaction was investigated both "in the flask" and by density functional theory (DFT) calculations. It was demonstrated that tetrahydrofuran derivatives with the benzoxime group (EWG = CHNOBn) are very good candidates for the subsequent highly stereoselective Grignard reaction.

Synthesis of sulfur containing macrocycles with sucrose scaffold.

The first synthesis of sucrose-based macrocycles containing two sulfur atoms in the ring was presented. The synthesis was initiated from known 6,6'-dideoxy-6,6'-di-chloro-1',2,3,3',4,4'-hexa-O-benzyl-sucrose in which both terminal positions (C6 and C6') were elongated by the -S-CH2-CH2-OH unit. The resulting diol was converted into dichloride and reacted further with a series of diamines which afforded the corresponding macrocyclic derivatives in high yields.

Synthesis of Cyclotriveratrylene-Sucrose-Based Capsules.

Cyclotriveratrylene (CTV) is a C3-symmetrical macrocycle, which can be used as a chiral building block in the construction of supramolecular containers. Coupling of the CTV unit with a sucrose molecule gave enantiopure water-soluble (after deprotection) containers. The absolute configuration of the synthesized capsules was determined by NMR and ECD spectroscopies and DFT calculations.

First synthesis of cryptands with sucrose scaffold.

Cryptands with sucrose scaffold, an unknown class of such derivatives, were prepared from the readily available 2,3,3',4,4'-penta-O-benzylsucrose and 1',2,3,3',4,4'-hexa-O-benzylsucrose.

"Choose-a-size" control in the synthesis of sucrose based urea and thiourea macrocycles.

Highly efficient synthesis of monomeric and dimeric thiourea macrocycles with a per-O-benzylated sucrose scaffold is reported. Application of flow synthesis results in exclusive formation of a monomer in 79% yield. Batch synthesis provides two isomeric dimers in 85% yield. Dimers are capable of anion binding via two thiourea groups acting cooperatively.

Synthesis of a sucrose-based macrocycle with unsymmetrical monosaccharides "arms".

An efficient methodology for the selective substitution of both terminal positions (C6 and C6') in 1',2,3,3',4,4'-hexa-O-benzylsucrose with different unsaturated monosaccharide units is presented. Such a highly functionalized intermediate was cyclized under RCM conditions to afford a macrocyclic derivative containing a 31-membered ring in 26% yield.

An efficient synthesis of a C12-higher sugar aminoalditol.

The C12-aminoalditol H2NCH2-(CHOBn)10-CH2OH was prepared from two simple monosaccharide building blocks. The synthesis was realized by a regioselective introduction of the azide group and subsequent protection-deprotection transformations. The chemical reactivity of the aminoalditol was tested in the reductive amination reaction with a selectively protected sucrose monoaldehyde.

Chloride-Templated Macrocyclization and Anion-Binding Properties of C2-Symmetric Macrocyclic Ureas from Sucrose.

A high-yielding, one-pot simultaneous synthesis and full characterization of two regioisomeric C2-symmetrical macrocycles 3a and 3b from triphosgene and readily available hexa-O-benzyl-6,6'-diaminosucrose 1 is reported. The efficient macrocyclization (90% overall yield, ∼1:1 ratio of 3a vs 3b) is attributed to favorable steric constraints and to a templation by a chloride anion. 1H NMR titration studies and theoretical predictions revealed that both receptors show similar affinity for acetate and benzoate anions and enhanced preference for chloride over H2PO4-.

Synthesis of aza-crown analogues and macrocyclic bis-lactams with sucrose scaffold.

2,3,3',4,4'-Penta-O-benzylsucrose was converted into the corresponding diaminoalcohol which was used as a key building block in the synthesis of the analogues of aza-crown ethers and bis-lactams.

Synthesis of polyhydroxylated pyrrolidines from sugar-derived bromonitriles through a cascade addition of allylmagnesium bromide/cyclization/reduction.

The synthesis of polyhydroxylated 2-allylpyrrolidines from sugar-derived bromonitriles in a cascade addition of allylmagnesium bromide/SN2 cyclization/reduction with Zn(BH4)2 is described. The stereochemical course of the reduction step is rationalized. Two of the obtained compounds are transformed into stereoisomers of naturally-occurring iminosugar (+)-lentiginosine. In an alternative approach, 2,2-diallylpyrrolidines are obtained from bromonitriles in a cascade addition of allylmagnesium bromide/SN2 cyclization/addition of another equivalent of allylmagnesium bromide.

Synthesis of polyhydroxylated decalins via two consecutive one-pot reactions: 1,4-addition/aldol reaction followed by RCM/syn-dihydroxylation.

Synthesis of novel polyhydroxylated derivatives of decalin is described. The presented methodology consists in a one-pot copper-catalyzed 1,4-addition of vinylmagnesium bromide to sugar-derived cyclohexenone, followed by an aldol reaction with a derivative of but-3-enal. The obtained diene is then subjected to an assisted tandem catalytic sequence: ring-closing metathesis with the subsequent reuse of the Ru-catalyst in the syn-dihydroxylation. The stereochemical outcome of these reactions is discussed.

Synthesis of octitols and the respective amino-derivatives from 'organo-aldols'.

Two diastereoisomeric keto-octoses, obtained in the reaction of 2,3:4,5-diacetone-D-arabinose with protected dihydroxyacetone catalyzed with L- or D-proline, were converted into octitols by stereoselective reduction of the carbonyl group with zinc borohydride and final deprotection. The study on the preparation of the respective amino-derivatives by reductive amination of these organo-adducts is presented; stereochemical aspects of these processes are discussed.

Nitrogen-containing macrocycles having a carbohydrate scaffold.

Nitrogen-containing macrocyclic compounds (amines, amides, and N-heterocyclic derivatives) are important targets in supramolecular chemistry. This chapter discusses the importance of aza-macrocycles in general and, in particular, those receptors containing sugar unit(s). The combination of a carbohydrate scaffold bearing nitrogen-containing functional groups in macrocyclic molecules opens a convenient route to chiral receptors having potentially useful properties. The carbohydrate-based macrocycles discussed are classified into several general groups: (1) aza-crown ethers containing a carbohydrate subunit, (2) cyclic homooligomers from amino sugars, (3) sugar-based cryptands, (4) cyclic peptides containing amino sugar units (including C2- and C3-symmetrical macrocyclic glycopeptides), (5) nitrogen- containing glycophanes, and (6) 1,2,3-triazoles containing synthetic cyclodextrin analogues. The general strategies employed, as well as specific ones leading to such complex derivatives, are surveyed. Applications of such carbohydrate receptors, pointing to their importance as hosts in supramolecular chemistry, are discussed.

Synthesis of a sucrose dimer with enone tether; a study on its functionalization.

The reaction of appropriately functionalized sucrose phosphonate with sucrose aldehyde afforded a dimer composed of two sucrose units connected via their C6-positions ('the glucose ends'). The carbonyl group in this product (enone) was stereoselectively reduced with zinc borohydride and the double bond (after protection of the allylic alcohol formed after reduction) was oxidized with osmium tetroxide to a diol. Absolute configurations of the allylic alcohol as well as the diol were determined by circular dichroism (CD) spectroscopy using the in situ dimolybdenum methodology.

Carboxybenzyl group as an o-nucleophile in the C-H allylic oxidation: total synthesis of (-)-castanospermine.

The first palladium-mediated C-H allylic oxidation with a Cbz group acting as an O-nucleophile is reported. It was found that this transformation is promoted by rare-earth metal triflates: Yb(OTf)(3) or Sc(OTf)(3). A possible catalytic cycle is proposed. This reaction was applied in the synthesis of a d-xylose derived oxazolidinon, a versatile intermediate used further in the stereoselective synthesis of unnatural (-)-castanospermine. Cyclization of the key intermediate with PhSeBr afforded the desired bicyclic scaffold. In an alternative route, hydroboration/oxidation followed by DPPA-mediated cyclization was used.

Synthesis of polyhydroxylated quinolizidines and azaspiro[4.5]decanes from D-xylose.

The synthesis of novel polyhydroxylated quinolizidines and azaspiro[4.5]decanes is reported. A key step of this transformation involved an addition of allylmagnesium bromide to an ω-bromonitrile derived from D-xylose followed by an intramolecular displacement of a bromide. The resulting cyclic imine was treated either with allylmagnesium bromide or with NaBH4, to provide 2,2-diallyl- or 2-allylpiperidine, respectively. The desired bicyclic framework was constructed via a ring-closing metathesis reaction. The Ru catalysts were reused in the following syn-dihydroxylation step.