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Using the palladium(II)-catalyzed oxidative cyclization of a diarylamine and the annulation of a dimethylpyran ring by Lewis acid promoted reaction with prenal as key steps, the total syntheses of the 6-oxygenated pyrano[3,2-a]carbazole alkaloids koenine and koenimbine, and of the 6,7-dioxygenated pyrano[3,2-a]carbazole alkaloids koenigine and koenigicine (koenimbidine, koenidine) were achieved. Moreover, these studies led to an improved synthetic route to the 2,6-dioxygenated carbazole alkaloid glycozolidol. Mukonicine, originally published as 6,8-dimethoxypyrano[3,2-a]carbazole, was found to be identical with koenigicine. [ABSTRACT FROM AUTHOR]

Desamino tyrosine (DAT) and desamino tyrosyl tyrosine (DATT) can be used to functionalize the end groups of water soluble polymers. The phenolic groups may enable physical interactions by p-p interaction and hydrogen bonds, which might lead to the formation of a hydrogel by physical crosslinking. However, using star-shaped oligo(ethylene glycols) (sOEG) with a molecular weight of 5 kDa for functionalization with DAT or DATT resulted in the formation of surfactants and not in hydrogels. As the molecular weight of the sOEG polymer chain can have an influence on forming physical cross links, DAT(T)- fuctionalization of sOEGs with higher molecular weight was investigated, the polymers were structurally characterized and for their mechanical properties were evaluated by rheological measurements. Aqueous solutions ofDAT(T)-sOEGs with 10 and 20 kDa showed lower storage and loss moduli compared to unfunctionalized sOEGs indicating also the formation of surfactants. Cell-based assays showed that all sOEG solutions did not impair cell viability and were free of endotoxins, which could otherwise induce uncontrolled immune responses. Conclusively, our data suggested that the sOEG solutions have surface active properties without inducing unwanted cellular responses, which is required e.g. in pharmaceutical applications to solubilize hydophobic substances. [ABSTRACT FROM AUTHOR]

Using a palladium(II)-catalyzed oxidative cyclization of an N,N-diarylamine, we have achieved the total synthesis of the 2,8-dioxygenated carbazole alkaloids carbalexin B, clausine A, clauszoline M, and 2,8-dihydroxy-3-methylcarbazole. [ABSTRACT FROM AUTHOR]

A Buchwald-Hartwig amination and palladium(II)-catalyzed oxidative cyclization reaction sequence provided efficient access to a series of oxygenated tricyclic carbazoles. In the present work, this approach was applied to the total syntheses of the naturally occurring carbazole alkaloids 2-hydroxy-7-methylcarbazole, glycozolicine, mukoline, mukolidine, sansoakamine, glycozolidine, clausine-H (clauszoline-C), clausine-K (clauszoline-J), and methyl 2-hydroxy-7-methoxycarbazole-3-carboxylate, which was originally proposed as the structure of clausine-TY. The synthesis of the latter led to the structural reassignment of clausine-TY. [ABSTRACT FROM AUTHOR]

The boronic acid-catalyzed annulation of citral opens up a short route to oxygenated cyclized monoterpenoid pyranocarbazole alkaloids. Thus, murrayamine-D is available in only three steps and 55% overall yield from the corresponding carbazole precursor. [ABSTRACT FROM AUTHOR]

Side chain functionalization of gelatin with tyrosine-derived moieties, desaminotyrosine (DAT) or desaminotyrosyl tyrosine (DATT), has been reported to lead to physical networks stabilized by aromatic interactions and hydrogen bonds, while the inherent ability of gelatin chains to organize in helices is suppressed. Here, the treatment of DAT and DATT gelatin films at defined temperatures (drying at 5 °C, freeze-drying, and freeze-thawing) were explored for the potential to additionally stabilize the hydrogels by increasing the content of helical domains as additional physical netpoints. The influence of the drying procedures on the hydrogel properties such as network morphology and mechanical properties were analyzed by WAXS, swelling, and rheological measurements. The triple helix content had a stabilizing effect on gelatin-based hydrogels at temperatures below the helix-to-coil transition. However, this effect was less pronounced at physiological conditions above the transition temperature, resulting in rapid dissolution of the physical gelatin networks. [ABSTRACT FROM AUTHOR]

Shape-memory polymers (SMPs) are stimuli-sensitive materials capable of performing complex movements on demand, which makes them interesting candidates for various applications, for example, in biomedicine or aerospace. This trend article highlights current approaches in the chemistry of SMPs, such as tailored segment chemistry to integrate additional functions and novel synthetic routes toward permanent and temporary netpoints. Multiphase polymer networks and multimaterial systems illustrate that SMPs can be constructed as a modular system of different building blocks and netpoints. Future developments are aiming at multifunctional and multistimuli-sensitive SMPs. [ABSTRACT FROM AUTHOR]

Purpose: The aromatic compounds desaminotyrosine (DAT) and desaminotyrosyltyrosine (DATT) have been successfully used to functionalize gelatin in order to form physically crosslinked networks via π-π interactions and hydrogen bonds of the introduced phenol moieties. Here, it was explored whether this concept can be applied to a synthetic polymer not engaging in additional interactions such as triple helix formation in gelatin, enabling a network to form by physical interactions mainly related to the terminal functional groups. Oligo(ethylene glycol) (OEG) was chosen as hydrophilic synthetic polymer for the backbone structure. Methods: Linear OEG (MP = 3 kDa) and four-arm OEG (Mn = 5 kDa) with amino functionalities as endgroups were functionalized with DAT and DATT using EDC·HCl and NHS as activating agents. The compounds were characterized by NMR, IR spectroscopy, and MALDI. Rheological behavior of aqueous solutions of the polymers was studied. The critical micelle concentration (CMC) was determined by a fluorescence spectroscopic analysis using the hydrophobic fluorescent dye pyrene. Results: DATT-functionalized linear OEG, four-arm DAT-functionalized OEG and four-arm DATT-functionalized OEG were synthesized with degrees of functionalization of 60-95 mol%. All compounds were water soluble, and rheological measurements revealed a decrease in storage modulus G' and loss modulus G'' compared to unfunctionalized OEG. Moreover, the CMC of linear OEG-DATT could be determined. Conclusions: The syntheses of OEG functionalized with the aromatic compounds DAT and DATT was reported. The polymers showed the properties of a surfactant. [ABSTRACT FROM AUTHOR]

The article reflects on the use of functional polymers in medicine. Topics include step for synthesis of block copolymer which involves ring-opening polymerization of N-carboxybenzyl-protected L-ornithine N-carboxyanhydride with methoxy-polyethylene glycol (PEG)-amine followed by quantitative guanidinylation; challenges related to release of bioactive substances in drug delivery research; and use of gold nanoparticles for making biosensors.

Shape-memory hydrogels (SMH) are multifunctional, actively-moving polymers of interest in biomedicine. In loosely crosslinked polymer networks, gelatin chains may form triple helices, which can act as temporary net points in SMH, depending on the presence of salts. Here, we show programming and initiation of the shape-memory effect of such networks based on a thermomechanical process compatible with the physiological environment. The SMH were synthesized by reaction of glycidylmethacrylated gelatin with oligo(ethylene glycol) (OEG) α,ω-dithiols of varying crosslinker length and amount. Triple helicalization of gelatin chains is shown directly by wide-angle X-ray scattering and indirectly via the mechanical behavior at different temperatures. The ability to form triple helices increased with the molar mass of the crosslinker. Hydrogels had storage moduli of 0.27–23 kPa and Young's moduli of 215–360 kPa at 4 °C. The hydrogels were hydrolytically degradable, with full degradation to water-soluble products within one week at 37 °C and pH = 7.4. A thermally-induced shape-memory effect is demonstrated in bending as well as in compression tests, in which shape recovery with excellent shape-recovery rates Rr close to 100% were observed. In the future, the material presented here could be applied, e.g., as self-anchoring devices mechanically resembling the extracellular matrix. [ABSTRACT FROM AUTHOR]

The author discusses the design of advanced functional polymers for medical purposes. Topics mentioned include the utilization of porous scaffolds for tissue reconstruction, the biomedical applications of thermosensitive hydrogels and the incorporation of nanoparticles into electrospun fibers through additive electrospraying.

A space filling model of the X‐ray structure of the pyrano[3,2‐a]carbazole alkaloid mupamine is shown. Its synthesis, which involves the boronic acid‐catalyzed annulation of citral, is described in the Communication by H.‐J. Knölker et al. on page 8536 ff. [ABSTRACT FROM AUTHOR]

Front Cover: Shape‐memory polymers can be created in a modular approach, consisting of three components: chain segments, permanent netpoints and temporary netpoints. Varying these components enables the integration of several functions, as well as the implementation of multistimuli‐sensitivity in shape‐memory polymers. Further details can be found in the article by Konstanze K. Julich‐Gruner, Candy Löwenberg, Axel T. Neffe, Marc Behl, and Andreas Lendlein* on page 527. [ABSTRACT FROM AUTHOR]