Nucleoside analogues from push-pull functionalized branched-chain pyranosides

The reaction of methyl 4,6-O-benzylidene-2-deoxy-α-D-erythro- hexopyranosid-3-ulose (1) with ethynylmagnesium bromide in tetrahydrofuran and subsequent trimethylsilylation yielded the methyl 4,6-O-benzylidene-2-deoxy-3-C- ethynyl-3-O-trimethylsilyl-α-D-ribo-hexopyranoside (3). Push-pull functionalization of 3 with N,N,N′,N′,N″,N″- hexamethylguanidinium chloride under basic conditions and following deprotection afforded the spiro{2,5-dihydro-3-dimethylamino-furan-2,8'-4',4'a,6',7',8',8'a- hexahydro-6'-methoxy-2'-phenyl-pyrano[3,2-d][1,3]dioxine}-5- ylidenemalononitrile (9). Furthermore, compound 1 reacted with N,N-dimethylformamide dimethylacetal to furnish methyl (E)-4,6-O-benzylidene-2- deoxy-2-dimethylaminomethylene-α-D-erythro-hexopyranosid-3-ulose (10). Treatment of 10 with methylhydrazine and amidines yielded (4S,5aR,8R,9aS)-2,5a, 6,9a-tetrahydro-4-methoxy-2-methyl-8-phenyl-4H-[1,3]dioxino[4',5':5,6]pyrano[4, 3-c]pyrazole (11a) and (2R,4aR,6S,10bS)-4,4a,6,10b-tetrahydro-6-methoxy-2- phenyl[1,3]dioxino[4',5':5,6]pyrano[4,3-d]pyrimidines 12, respectively. © 2006 Verlag der Zeitschrift für Naturforschung

Novel room temperature ionic liquids of hexaalkyl substituted guanidinium salts for dye-sensitized solar cells

A novel family of room temperature ionic liquids, N,N-diethyl-N′,N′-dipropyl-N′′-hexyl-N′′-methylguanidinium iodide (SGI) and N,N,N′,N′-tetramethyl-N′′,N′′-dipentylguanidinium tricyanomethanide (SGTM) were designed and synthesized. Due to the strong charge delocalization on the tricyanomethanide anion and, thus, weaker ion-pairing, SGTM has a lower viscosity than SGI salt that has iodide as an anion. SGI was successfully used as an iodide resource for dye-sensitized nanocrystalline solar cells. The device with a solvent-free, SGI-based electrolyte achieved a 5.9% power conversion efficiency under an air mass 1.5 incident light of 9.47mW/cm

The role of peptides in bone healing and regeneration: A systematic review

Background: Bone tissue engineering and the research surrounding peptides has expanded significantly over the last few decades. Several peptides have been shown to support and stimulate the bone healing response and have been proposed as therapeutic vehicles for clinical use. The aim of this comprehensive review is to present the clinical and experimental studies analysing the potential role of peptides for bone healing and bone regeneration. Methods: A systematic review according to PRISMA guidelines was conducted. Articles presenting peptides capable of exerting an upregulatory effect on osteoprogenitor cells and bone healing were included in the study. Results: Based on the available literature, a significant amount of experimental in vitro and in vivo evidence exists. Several peptides were found to upregulate the bone healing response in experimental models and could act as potential candidates for future clinical applications. However, from the available peptides that reached the level of clinical trials, the presented results are limited. Conclusion: Further research is desirable to shed more light into the processes governing the osteoprogenitor cellular responses. With further advances in the field of biomimetic materials and scaffolds, new treatment modalities for bone repair will emerge

3. Fachtagung Iminiumsalze

Available from TIB Hannover / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Formylation of activated arenes by phenyl formate: implications for the mechanism of the Fries rearrangement of aryl formates

We present an NMR and DFT investigation of the reaction of phenyl formate with 3-methoxyphenol and 3,5-dimethoxyphenol with excess BCl3. The products obtained (3-methoxy- and 3,5-dimethoxy-salicylaidehyde, respectively) are the same as those resulting from the Fries rearrangement of 3-methoxy- and 3,5-dimethoxy-phenyl formate. These results represent a novel regioselective synthetic route to aromatic aldehydes, using phenyl formate as a source of formylating agent. They also unambiguously prove that the Fries rearrangement of aryl formates (that we recently investigated in J. Org. Chem. 71, 9331-9340, 2006) is intermolecular: the intermediate formyl chloride is released in situ and, in turn, it formylates the intermediate dichloroborate ester of 3-methoxy- and 3,5-dimethoxy-phenol in a second independent step. The -BCl2 moiety bound to the aryl oxygen of the substituted phenol interacts with formyl chloride strongly favouring the ortho substitution

Neue, umweltfreundliche, gewerbetoxikologisch unbedenkliche Aldehydsynthesen (Varianten der Vilsmeier-Haack-Reaktion) Abschlussbericht

Available from TIB Hannover: F99134+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman

FRIES REARRANGEMENT OF ARYL FORMATES PROMOTED BY BCL3. MECHANISTIC EVIDENCE FROM 11B NMR SPECTRA AND DFT CALCULATIONS

The Fries rearrangement of model aryl formate esters, promoted by boron trichloride, has been investigated by means of NMR spectroscopy (both experimental and computational) and by DFT calculations. Firstly, the B-11 NMR chemical shifts of a series of model boron compounds have been predicted by GIAO-B3LYP/6-31G(d,p) calculations, in order to make predictions of the chemical shifts of transient reaction intermediates observable by B-11 NMR. Such B-11 spectra for the reaction of two esters (phenyl and 3-methyoxyphenyl formates) have been obtained, and are found to follow different patterns which can be rationalized on the basis of computed chemical shifts. Secondly, DFT calculations (B3LYP/6-31G(d,p) level) have been employed to investigate several mechanistic pathways of the rearrangement of phenyl formate. It is found that the pathways leading to the lowest activation energies are those in which formyl chloride is generated from a complex between phenyl formate and BCl3, which then acts as the formylating agent

Nucleoside Analogues from Push-Pull Functionalized Branched-Chain Pyranosides

The reaction of methyl 4,6-O-benzylidene-2-deoxy-α-D-erythro- hexopyranosid-3-ulose (1) with ethynylmagnesium bromide in tetrahydrofuran and subsequent trimethylsilylation yielded the methyl 4,6-O-benzylidene-2-deoxy-3-C- ethynyl-3-O-trimethylsilyl-α-D-ribo-hexopyranoside (3). Push-pull functionalization of 3 with N,N,N′,N′,N″,N″- hexamethylguanidinium chloride under basic conditions and following deprotection afforded the spiro{2,5-dihydro-3-dimethylamino-furan-2,8'-4',4'a,6',7',8',8'a- hexahydro-6'-methoxy-2'-phenyl-pyrano[3,2-d][1,3]dioxine}-5- ylidenemalononitrile (9). Furthermore, compound 1 reacted with N,N-dimethylformamide dimethylacetal to furnish methyl (E)-4,6-O-benzylidene-2- deoxy-2-dimethylaminomethylene-α-D-erythro-hexopyranosid-3-ulose (10). Treatment of 10 with methylhydrazine and amidines yielded (4S,5aR,8R,9aS)-2,5a, 6,9a-tetrahydro-4-methoxy-2-methyl-8-phenyl-4H-[1,3]dioxino[4',5':5,6]pyrano[4, 3-c]pyrazole (11a) and (2R,4aR,6S,10bS)-4,4a,6,10b-tetrahydro-6-methoxy-2- phenyl[1,3]dioxino[4',5':5,6]pyrano[4,3-d]pyrimidines 12, respectively. © 2006 Verlag der Zeitschrift für Naturforschung