Overexpression of a Sugarcane BAHD Acyltransferase Alters Hydroxycinnamate Content in Maize Cell Wall

The purification of hydroxycinnamic acids [p-coumaric acid (pCA) and ferulic acid (FA)] from grass cell walls requires high-cost processes. Feedstocks with increased levels of one hydroxycinnamate in preference to the other are therefore highly desirable. We identified and conducted expression analysis for nine BAHD acyltransferase ScAts genes from sugarcane. The high conservation of AT10 proteins, together with their similar gene expression patterns, supported a similar role in distinct grasses. Overexpression of ScAT10 in maize resulted in up to 75% increase in total pCA content. Mild hydrolysis and derivatization followed by reductive cleavage (DFRC) analysis showed that pCA increase was restricted to the hemicellulosic portion of the cell wall. Furthermore, total FA content was reduced up to 88%, resulting in a 10-fold increase in the pCA/FA ratio. Thus, we functionally characterized a sugarcane gene involved in pCA content on hemicelluloses and generated a C4 plant that is promising for valorizing pCA production in biorefineries.

Studies on the Properties of the Sporulation Specific Protein Dit1 and Its Product Formyl Tyrosine

The dityrosine layer is a unique structure present in the spore wall of the budding yeast Saccharomyces cerevisiae. The primary constituent of this layer is bisformyl dityrosine. A sporulation-specific protein, Dit1 is localized in the spore cytosol and produces a precursor of bisformyl dityrosine. Although Dit1 is similar to isocyanide synthases, the loss of Dit1 is not rescued by heterologous expression of the Pseudomonas aeruginosa isocyanide synthase, PvcA, indicating that Dit1 does not mediate isocyanidation. The product of Dit1 is most likely formyl tyrosine. Dit1 can produce its product when it is expressed in vegetative cells; however, formyl tyrosine was not detected in the crude cell lysate. We reasoned that formyl tyrosine is unstable and reacts with some molecule to form formyl tyrosine-containing molecules in the cell lysate. In support of this hypothesis, formyl tyrosine was detected when the lysate was hydrolyzed with a mild acid. The same property was also found for bisformyl dityrosine. Bisformyl dityrosine molecules assemble to form the dityrosine layer by an unknown mechanism. Given that bisformyl dityrosine can be released from the spore wall by mild hydrolysis, the process of formyl tyrosine-containing molecule formation may resemble the assembly of the dityrosine layer.

Pd/C-CATALISED HYDROGENIZATION OF METHYL PYRROLE-3-CARBOXYLATES IN THE DIASTEREOSELECTIVE SYNTHESIS OF α-SUBSTITUTED β-PROLINES

The analysis of synthetic and biological importance of α-substituted β-prolines was conducted. Methods of synthesis of β-prolines and their esters, based on both intra- and intermolecular reactions of formation of functionalized pyrrolidinic cycle, as well as catalytic reduction of corresponding 2,3-substituted pyrroles and their dihydro derivatives, were systematized. The necessity of the hydrogenation process improvement of 2,3-di-substituted pyrroles using cheap catalysts was justified. The approach to α-substituted β-prolines (2-substituted pyrrolidine-3-carboxylic acids) was pro-posed, the first stage of which is N-Boc-protection of 2-substituted pyrrolidine-3-carboxylates with di-tert-butyl dicarbonate (Boc-anhydride) in the dichloromethane solution at the room temperature in presence of catalytic amounts of N,N-dime-thylaminopyridine. Obtained derivatives were subjected to hydrogenation in the autoclave at 45 atm. at 40 oC for 20 hours in presence of 10 % Pd/C catalyst. It was found, that reaction at such conditions proceeds with the full conversion of starting compounds and demonstrates high stereoselec-tivity and leads to the mixture of diastereomeric N-Boc-protected pyrrolidine-3-carboxylates of cis- and trans-configurations with corresponding contents of 84–87 % and 13–16 % according to NMR 1Н and chromato-mass spectra. The mild hydrolysis of isolated reaction mixtures in the water solution of lithium hydroxide followed by neutrali-zation and N-Boc-deprotection with 15 % hydrochloric acid allows isolating pure major diaste-reomers of α-substituted β-prolines with 69–74 % yields. Their trans-configuration was reliably confirmed by NMR 1Н spectroscopy using the NOESY experiment.

Preparation of pH-Responsive Poly(aspartic acid) Nanogels in Inverse Emulsion

Poly(aspartic acid) (PASP) hydrogels were prepared by cross-linking polysuccinimide (PSI) with diaminobutane followed by the mild hydrolysis of the resultant PSI gels to PASP hydrogels. The composition dependence of the gelation time and the stiffness of bulk PASP hydrogels were determined by rheometry and compression tests, respectively. The composition of the prepared PASP nanogels was chosen based on the results on bulk PASP hydrogels. Prior to nanogel preparation stability of DMSO-in-oil (inverse) emulsions was tested as a function of the chemical quality of apolar phase, the concentration of the precursor polymer and the concentration of the surfactant. PASP nanogels in the size of a few hundred nanometers were prepared by the hydrolysis of PSI nanogels synthesized in inverse emulsion. PASP nanogels showed pH-dependent swelling and strongly negative surface charge at physiological pH values, thus they can be further developed to meet the specific criteria of different bio-related applications.

Midinfrared FT-IR as a Tool for Monitoring Herbaceous Biomass Composition and Its Conversion to Furfural

A semiquantitative analysis by means of midinfrared FT-IR spectroscopy was tuned for the simultaneous determination of cellulose, hemicellulose, and lignin in industrial crops such as giant reed (Arundo donaxL.) and switchgrass (Panicum virgatumL.). Ternary mixtures of pure cellulose, hemicellulose, and lignin were prepared and a direct correlation area/concentration was achieved for cellulose and lignin, whereas indirect correlations were found for hemicellulose quantification. Good correspondences between the values derived from our model and those reported in the literature or obtained according to the official Van Soest method were ascertained. Average contents of 40–45% of cellulose, 20–25% of hemicellulose, and 20–25% of lignin were obtained for different samples of giant reed species. In the case of switchgrass, a content of 36% of cellulose, 28% of hemicellulose, and 26% of lignin was achieved. This analysis was also carried out on giant reed and switchgrass residues after a mild hydrolysis step carried out with dilute hydrochloric acid for the production of furfural with good yield. Reasonable compositional data were obtained, thus allowing an indirect monitoring which helps the optimization of the hydrothermal pretreatment for furfural production from hemicellulose fractions.

Preparation of thickness-tunable BiOCl nanosheets with high photocatalytic activity for photoreduction of CO2

BiOCl nanosheets with different percentages of exposed {001} facets were prepared via mild hydrolysis by a controlled facile hot injection technique, which exhibited relatively high activity for photocatalytic reduction of CO2 to CH4.

The Tanino Synthesis of (-)-Glycinoeclepin A

(-)-Glycinoeclepin A 3 is effective at pg/mL concentrations as a hatch-stimulating agent for the soybean cyst nematode. Approaching the synthesis of 3, Keiji Tanino of Hokkaido University envisioned (Chemistry Lett. 2010, 39, 835) the convergent coupling of the allylic tosylate 2 with the bridgehead anion 1. The assembly of the fragment 2 was particularly challenging, because the synthesis would require not just the establishment of the two adjacent cyclic quaternary centers but also control of the relative configuration on the sidechain. The preparation of 1 began with the prochiral diketone 3. Enantioselective reduction of the mono enol ether 4 set the absolute configuration of 5. Iodination followed by cyclization then completed the assembly of 1. The construction of the bicyclic tosylate 2 began with m-methyl anisole 7. Following the Rubottom procedure, Birch reduction followed by mild hydrolysis gave the ketone 8. Epoxidation followed by β-elimination delivered the racemic 9, which was exposed to lipase to give, after seven days, the residual alcohol in 40% yield and high ee. The sidechain nitrile was prepared from the diol 12. Homologation gave the nitrile 14, which was equilibrated to the more stable enol ether 15. The two cyclic quaternary centers of 3 were set in a single step by the conjugate addition of the anion of 16 to the crystalline enone 11. Mild hydrolysis of 17 gave the keto aldehyde, which underwent aldol condensation to give the enone 18. The hydroboration of 19 followed by coupling of the intermediate organoborane with 20 delivered 21 with 94:6 relative diastereocontrol. Formylation of the enone 22 followed by triflation and reduction then led to 2. Altough the ketone 1 could be deprotonated with LDA, the only product observed, even at –78°C, was the derived aldol dimer. The metalated dimethylhydrazone 25, in contrast, coupled smoothly with 2 to give, after hydrolyis, the desired adduct 26. Pd-mediated carboxylation of the enol triflate followed by selective oxidative cleavage and hydrolysis then completed the synthesis of (-)-glycinoecleptin A 3.