1.Theory of the milieu dependent isomerisation dynamics of reducing sugars applied to d-erythrose.
Kaufmann M1, Mügge C2, Kroh LW3. Carbohydr Res. 2015 Dec 11;418:89-97. doi: 10.1016/j.carres.2015.10.010. Epub 2015 Oct 30.
Quantitative (1)H selective saturation transfer NMR spectroscopy ((1)H SST qNMR) was used to fully describe the milieu dependent dynamics of the isomeric system of d-erythrose. Thermodynamic activation parameters are calculated for acidic as well as for basic catalysis combining McConnell's modified Bloch equations for the chemical exchange solved for the constraint of saturating the non-hydrated acyclic isomer, the Eyring equation and Hudson's equation for pH dependent catalysis. A detailed mathematical examination describing the milieu dependent dynamics of sugar isomerisation is provided. Thermodynamic data show evidence that photo-catalysed sugar isomerisation as well as degradation has to be considered. Approximations describing the pH and temperature dependence of thermodynamic activation parameters are derived that indicate the possibility of photo-affecting equilibrium constants. Moreover, the results show that isomerisation dynamics are closely related to degradation kinetics and that sugars' reactivities are altered by the concentration of acyclic carbonyl isomer and the sum of its ring closing rate constants.
2.Total facial selectivity of a d-erythrosyl aromatic imine in [4π + 2π] cycloadditions; synthesis of 2-alkylpolyol 1,2,3,4-tetrahydroquinolines.
Ferreira J1, Duarte VC1, Noro J1, Gil Fortes A1, Alves MJ1. Org Biomol Chem. 2016 Mar 1;14(10):2930-7. doi: 10.1039/c5ob02594j.
Different electron-rich dienophiles were combined with the imine obtained from 2,4-O-benzylidene-d-erythrose and p-anisidine furnishing enantiomerically pure tetrahydroquinolines, by inverse electron-demand [4π + 2π] cycloaddition. The imine was also reacted with 2-substituted electron-rich 1,3-butadienes giving the diastereomeric pure product, resulting from the normal electron demand cycloaddition. The facial selectivity of both processes is proposed on the basis of a 1,4-relationship between the hydroxyl group and the nitrogen atom in the chiral N-(p-methoxyphenyl)imine derivative.
3.Tautomers of Gas-Phase Erythrose and Their Interconversion Reactions: Insights from High-Level ab Initio Study.
Szczepaniak M1, Moc J1. J Phys Chem A. 2015 Nov 5;119(44):10946-58. doi: 10.1021/acs.jpca.5b07720. Epub 2015 Oct 22.
D-Erythrose is a C4 monosaccharide with a biological and potential astrobiological relevance. We have investigated low-energy structures of d-erythrose and their interconversion in the gas phase with the highest-level calculations up-to-date. We have identified a number of structurally distinct furanose and open-chain isomers and predicted α ↔ α and β ↔ β furanose interconversion pathways involving the O-H rotamers. We have estimated relative Gibbs free energies of the erythrose species based on the CCSD(T)/aug-cc-pVTZ electronic energies and MP2/aug-cc-pVTZ vibrational frequencies. By using natural bond orbital theory we have also quantified a stabilization of erythrose conformers and interconversion transition states by intramolecular H-bonds.
4.Biosynthesis of 2-deoxysugars using whole-cell catalyst expressing 2-deoxy-D-ribose 5-phosphate aldolase.
Li J1, Yang J, Men Y, Zeng Y, Zhu Y, Dong C, Sun Y, Ma Y. Appl Microbiol Biotechnol. 2015 Oct;99(19):7963-72. doi: 10.1007/s00253-015-6740-9. Epub 2015 Jun 24.
2-Deoxy-D-ribose 5-phosphate aldolase (DERA) accepts a wide variety of aldehydes and is used in de novo synthesis of 2-deoxysugars, which have important applications in drug manufacturing. However, DERA has low preference for non-phosphorylated substrates. In this study, DERA from Klebsiella pneumoniae (KDERA) was mutated to increase its enzyme activity and substrate tolerance towards non-phosphorylated polyhydroxy aldehyde. Mutant KDERA(K12) (S238D/F200I/ΔY259) showed a 3.15-fold improvement in enzyme activity and a 1.54-fold increase in substrate tolerance towards D-glyceraldehyde compared with the wild type. Furthermore, a whole-cell transformation strategy using resting cells of the BL21(pKDERA12) strain, containing the expressed plasmid pKDERA12, resulted in increase in 2-deoxy-D-ribose yield from 0.41 mol/mol D-glyceraldehyde to 0.81 mol/mol D-glyceraldehyde and higher substrate tolerance from 0.5 to 3 M compared to in vitro assays.