Selective Halogenation at Primary Positions of Cyclomaltooligosaccharides and a Synthesis of Per‐3,6‐anhydro Cyclomaltooligosaccharides

Abstract

0 . 0 0.1 0 . 2 0 . 3 0 . 4 A ( t ) -Fig. 3. Absorption at time I + dr vs absorption at time I for the photoreaction from the open to the closed photochromic form in toluene (A, , , = 496 nrn; copolyacrylate 5a with 9.4 mol % fulgimide groups).microscope observations have already revealed that irradiation of the materials with UV light leads to a higher clearing point of the meso phase. This suggests that the dihydrobenzofuran side groups (colored form) distort the parallel arrangement of the molecules in the meso phase less that the fulgimide groups. 0.1 1 2'0 4'0 6 0 ' S O '-00 t Chl -Fig. 4. Thermal stability of the colored form of the fulgimide groups in a copolymethacrylate 5 b with 2.5 mol% fulgimide content at 22 "C and 60 "C. A UV-irradiated film was used.To test the possibility of recording optical information, a film of a photochromic polymer was covered with a standard photomask and irradiated with UV light (k = 366 nm). The optically stored image of the mask could be observed with the polarizing microscope. Moreover, preliminary experiments have already shown that holographic patterns can be stored in the materials described here. The exact contribution of amplitude and phase effects is currently being investigated. Experimental Procedure1 was prepared by reaction of (E)/(Z)-2-[1-(2,5-dimethyl-3-furyl)ethylidene]-3isopropylidenesuccinic anhydride with ammonia in acetone solution [6,7]. 6-Hydroxyhexylacrylate 2a (R = H) and 6-hydroxyhexylmethacrylate 2 b (R = CH,) were synthesized as described in reference [lo]. Typical example of the procedure for 3a and 3b: 0.115 g of 1, 0.157 g of triphenylphosphane and 0.108 g of 2a were dissolved in dry THF. To this a solution of azodicarboxylate (0.108 g) in dry THF was added. A trace ofp-benzoquinone was also added to inhibit polymerization. The mixture was stirred for 14 hours in the dark. Afterwards the solvent was removed under vacuum and the product purified by flash chromatography (petrol ether: ethyl acetate 12:l). Yields: 3a 40.4% 3 b 29.3% (based on 1); oily compounds. All compounds have been characterized by IR, I3C and 'H NMR spectroscopy. 3a: 'HNMR (CDCI,, 400MHz): 6 =6.33 (m; Z-H of CH,=), 6.06 (t; H,C=CH), 5.87 (s; furan-H), 5.78 (m; E-H of CH,=), 4.11 (t; H,C-OOC), 3.55 (ti CH,-N), 2.54 ( s ; CH3-C=), 2.28 (S; 2-CH, of (CH,),C=), 2.20 ( s ; furan-5-CH3), 1.94 (s; furan-2-CH3), 1.64, 1.37 (m; N-CHI-(CHJ-CHI-OOC), 1.28 (s; E-CH, of (CH,),)C=). 3b: 'HNMR (CDCI,. 400MHz): 6 = 6.06 (m; Z-H of CH,=), 5.88 (s; furan-H), 5.52 (m; E-H of CH,=), 4.10 (ti CH,-OOC), 3.55 (ti CHI-N), 2.54 (s; CH3-C=). 2.28 (s; Z-CH3 of (CH,),C=); 2.21 (s; furan-5-CH3); 1.95 (s; furan-2-CH3); 1.91 (t; H,C=CCH,). 1.64. 1.37 (m; N-CHI-(CH,),-CH,-OOC), 1.28 (s; E-CH, ofThe mesogenic monomers 4 were prepared by standard methods [ l l , 121. The copolymers 5 were prepared by polymerization of the monomer (20-30 percent in THF solution) with 1.2 mol % of 2,2'-azohis(isobutyronitrile) at 55°C. The polymers were precipitated in methanol, purified by reprecipitation and dried under vacuu...

Cerebral Blood Volume Quantification in a C6 Tumor Model Using Gadolinium per (3,6-Anhydro) α-Cyclodextrin as a New Magnetic Resonance Imaging Preclinical Contrast Agent

“…The starting compound was hexakis (3,6-anhydro)-cyclomaltohexaose, simply denoted as per (3,6-anhydro)-a-cyclodextrin and synthesized according to a previously described procedure (Gadelle and Defaye, 1991). Hexakis (2-O-carboxymethyl-3,6-anhydro)-a-cyclodextrin, named ACX ( Figure 6A), was obtained in one step in the form of its hydrated sodium salt by substituting the residual hydroxyl groups of per (3,6-anhydro)-a-cyclodextrin by carboxymethyl groups as follows.…”

“…The hexakis (2-O-carboxymethyl-3,6-anhydro)-a-cyclodextrin, a hexaacid ACXH 6 cyclodextrin derivative named ACX, was recently synthesized after chemical modification of the native cyclodextrin (Gadelle and Defaye, 1991). It has the shape of a rather flat disc and a molecular weight of 1,464 Da.…”

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

“…[2,25,26]). These intermediates are then used to form persubstituted 6-deoxy-6-NH 2 -CDs (e.g., see ref.…”

“…[32,33]). The reaction conditions used in the last step are, again, typically very similar, and quite harsh [25][26][27][28][29][30][31][32][33].…”

Efficient and Versatile Modification of the Secondary Face of Cyclodextrins through Copper‐Catalyzed Huisgen 1,3‐Dipolar Cycloaddition

“…The primary face hydroxy groups are often transformed into good leaving groups, such as a tosylate [31] or halogen, [32] and further derivatizations are carried out by nucleophilic substitutions. Persubstitution of the secondary face is more difficult because of the higher degree of steric crowding.…”