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Novel Cyclic (novel + cyclic)
Selected AbstractsNovel Cyclic 1,2-Diacetals Derived from (2R,3R)-(+)-Tartaric Acid: Synthesis and Application as N,O Ligands for the Enantioselective Alkylation of Benzaldehyde by DiethylzincEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 8 2004M. Teresa Barros Abstract A chiral cyclic 1,2-diacetal derived from tartaric acid was used as the basic structural unit for novel ligands. Monooxazoline carbinols in which the degree of substitution of the alcohol and the nature of the stereocentre in the oxazoline ring were varied were synthesized in moderate to good yields. The influence of these structural factors on asymmetric induction was examined in the enantioselective addition of diethylzinc to benzaldehyde. Up to 60% ee was observed with a secondary or a tertiary alcohol as the metal-chelating group. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Aliphatic poly(ester-carbonate)s bearing amino groups and its RGD peptide graftingJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 21 2008Xiuli Hu Abstract This article deals with (1) synthesis of novel cyclic carbonate monomer (2-oxo [1,3]dioxan-5-yl)carbamic acid benzyl ester (CAB) containing protected amino groups; (2) ring-opening copolymerization of the cyclic monomer with L -lactide (LA) to provide novel degradable poly(ester-carbonate)s with functional groups; (3) removal of the protective benzyloxycarbonyl (Cbz) groups by catalytic hydrogenation to afford the corresponding poly(ester- co -carbonate)s with free amino groups; (4) grafting of oligopeptide Gly-Arg-Gly-Asp-Ser-Tyr (GRGDSY, abbreviated as RGD) onto the copolymer pendant amino groups in the presence of 1,1,-carbonyldiimidazole (CDI). The structures of P(LA- co -CA/RGD) and its precursor were confirmed by 1H NMR analysis. Cell experiments showed that P(LA- co -CA/RGD) had improved adhesion and proliferation behavior. Therefore, the novel RGD-grafted block copolymer is promising for cell or tissue engineering applications. © Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7022,7032, 2008 [source] Synthesis of a novel cyclic 5-membered dithiocarbonate (DTC) having hydroxy group and its application to terminal functionalization of polyurethaneJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 16 2005Suguru Motokucho A novel 5-membered cyclic dithiocarbonate (DTC) having a hydroxy group, 5-hydroxymethyl-1,3-oxathiolane-2-thione (DTC-OH), was synthesized from glycidol. On the basis of the highly efficient reaction of its hydroxyl group with isocyanate, a polyurethane having isocyanate terminals was modified with DTC-OH into a new type of polyurethane prepolymer having DTC-terminals, which was highly reactive with amines but tolerant to moisture. [source] Template-Directed Synthesis of Multiply Mechanically Interlocked Molecules Under Thermodynamic ControlCHEMISTRY - A EUROPEAN JOURNAL, Issue 16 2005Fabio Aricó Dr. Abstract The template-directed construction of crown-ether-like macrocycles around secondary dialkylammonium ions (R2NH2+) has been utilized for the expedient (one-pot) and high-yielding synthesis of a diverse range of mechanically interlocked molecules. The clipping together of appropriately designed dialdehyde and diamine compounds around R2NH2+ -containing dumbbell-shaped components proceeds through the formation, under thermodynamic control, of imine bonds. The reversible nature of this particular reaction confers the benefits of "error-checking" and "proof-reading", which one usually associates with supramolecular chemistry and strict self-assembly processes, upon these wholly molecular systems. Furthermore, these dynamic covalent syntheses exploit the efficient templating effects that the R2NH2+ ions exert on the macrocyclization of the matched dialdehyde and diamine fragments, resulting not only in rapid rates of reaction, but also affording near-quantitative conversion of starting materials into the desired interlocked products. Once assembled, these "dynamic" interlocked compounds can be "fixed" upon reduction of the reversible imine bonds (by using BH3,THF) to give kinetically stable species, a procedure that can be performed in the same reaction vessel as the inital thermodynamically controlled assembly. Isolation and purification of the mechanically interlocked products formed by using this protocol is relatively facile, as no column chromatography is required. Herein, we present the synthesis and characterization of 1) a [2]rotaxane, 2) a [3]rotaxane, 3) a branched [4]rotaxane, 4) a bis [2]rotaxane, and 5) a novel cyclic [4]rotaxane, demonstrating, in incrementally more complex systems, the efficacy of this one-pot strategy for the construction of interlocked molecules. [source] | ||||||||||