From glycerol to value-added products

Today, industrial plants that produce glycerol are closing down and others are opening that use glycerol as a raw material, owing to the large surplus of glycerol formed as a by-product during the production of biodiesel. Research efforts to find new applications of glycerol as a low-cost feedstock for functional derivatives have led to the introduction of a number of selective processes for converting glycerol into commercially valued products. This Minireview describes a selection of such achievements and shows how glycerol will be a central raw material in future chemical industries.     

Stereoselective synthesis of 2,3-unsaturated-aza-O-glycosides via new diastereoisomeric N-Cbz-imino glycal-derived allyl epoxides

Diastereoisomeric D,L-N-Cbz-imino glycal-derived allyl epoxides 5 and 6 have been synthesized, and their addition reactions with alcohols examined. The reactions lead to the corresponding 2,3-unsaturated-aza-O-glycosides through a new, completely regioselective 1,4-addition process which proceeds with complete substrate-dependent stereoselectivity.     

The chemical effects of molecular sol-gel entrapment

Chemical conversions within the cages of doped sol-gel porous oxides take place with unique advantages over reactions in solution as the glassy matrix has tremendous effects on the reactivity of the entrapped molecules. The chemical properties of sol-gel materials can be tailored in an immense range of values and chemists are increasingly achieving control on reactions taking place within these matrices, including crucially important photovoltaics. Highlighting recent major advancements, we show in this tutorial review how this is actually taking place.     

PCB-based integration of electrochemiluminescence detection for microfluidic systems

This communication presents an instrumental development based on the printed circuit board (PCB) technology to integrate electrochemiluminescence (ECL) analysis in microfluidic systems. PCB gold macro- (10 mm2) and micro- (0.09 mm2) electrodes and two ECL microfluidic devices are designed, fabricated and tested via luminol ECL detection. Potential modulation is performed between 0.7 and 0 V vs. Ag/AgCl for luminol oxidation, thus giving rise to on/off ECL responses in the presence of hydrogen peroxide. Synchronous detection is adopted to allow weak ECL signal recovery at a very low signal-to-noise ratio (SNR). The detection limit obtained with the two ECL microfluidic devices is 50 nM and 100 nM H2O2 for macroelectrodes and microelectrodes, respectively.     

Characterization of the protein profile of donkey's milk whey fraction

Characterization of the protein profile of the whey fraction from a milk sample taken from an individual donkey belonging to the 'Ragusana' species of the East of Sicily is reported. Direct RP-HPLC/electrospray ionization (ESI)-MS analysis of the whey fraction allowed the detection of some unknown components, together with the identification of already known whey proteins. Matrix-assisted laser desorption/ionization (MALDI)-TOF/MS and RP-HPLC/ESI-MS/MS analysis of the enzymatic digests of the unknown components resulted the identification and characterization of (1) two beta-casein fragments; (2) the sequence of donkey's serum albumin; and (3) the oxidized methionine forms of lysozyme B and alpha-lactoalbumin. One of the two beta-casein fragments corresponds to the sequence Val(176)-Arg(189) of the horse's beta-casein. The second one corresponds the C-terminal sequence Tyr(199)-Val(226) of the horse's beta-casein, with four amino acid substitutions (Q --> R(203), L/I --> P(206), F --> L(210) and P --> A(219)). Both fragments, reasonably arising by endogenous proteases cleavage of the donkey's beta-casein, could be potential biologically active peptides. Direct mass spectrometric sequence characterization of the detected donkey's serum albumin reveals the presence of the amino acid substitution Val --> Ile at position 497 with respect to the cDNA deduced sequence. The oxidized forms of lysozyme B and alpha-lactoalbumin are selectively oxidized at methionine 79 and methionine 90, respectively.     

New insight into the reaction of singlet oxygen with sulfur-containing cyclic alkenes: dye-sensitized photooxygenation of 5,6-dihydro-1,4-dithiins

The reaction of 3-methyl-5,6-dihydro-1,4-dithiins with singlet oxygen affords dicarbonyl compounds and/or ring-contracted ketosulfoxides, the latter regio- and stereoselectively, depending on the nature of the substituent at C-2 and on the reaction conditions. In competition with normal fragmentation, the intermediate dioxetanes, derived from [2 + 2] cycloaddition of singlet oxygen to the double bond, undergo an intramolecular oxygen transfer to the sulfur-1 atom, leading to labile epoxide intermediates. The latter convert to cis- and trans-ketosulfoxides through a non-concerted S-4 migration. This pathway is promoted by the electron-withdrawing group at C-2 and, for monosubstituted amide, by the solvent basicity. S-Oxidation of dithiins is insignificant, except for the monosubstituted amide derivative or in the presence of protic species, and occurs selectively at the S-1 atom.     

Photoreactivity of triazolopyridinones, including the drug trazodone, in aqueous solution

Irradiation of triazolo[4,3-a]pyridin-3-ones at 310 nm has been investigated in water/acetonitrile (7%). Cis-cisoid-fused cyclobutanes are generally obtained. Cage products are found starting from derivatives bearing (piperazin-1-yl)aryl moiety under dilute conditions (10⁻³ M). Two different routes appear to be involved in the formation of the observed photoproducts. A plausible mechanistic explanation is reported.     

Synthesis and evaluation as NOP ligands of some spiro[piperidine-4,2'(1'H)-quinazolin]-4'(3'H)-ones and spiro[piperidine-4,5'(6'H)-[1,2,4]triazolo[1,5-c]quinazolines

Some spiro[piperidine-4,2'(1'H)-quinazolin]-4'(3'H)-ones 3 and spiro[piperidine-4,5'(6'H)-[1,2,4]triazolo[1,5-c]quinazolines] 4 were synthesized and evaluated as ligands of the nociceptin receptor. The examined compounds showed partial agonistic activity, except compounds 3, 4n that proved to be pure antagonists.