No abstract

The liquefaction of lignocellulose is strongly affected by the choice of the liquefaction solvent. This effect was studied by processing pinewood at 310 °C in various organic solvents, including some refinery streams. The impact on yields of char, biocrude, and gas was determined. The resulting biocrude was analyzed with GPC and GC-MS, the solid residue with FTIR and HR-SEM, and the gas with GC. The solvents appeared to influence the liquefaction through interaction with early carbohydrate degradation products rather than interaction with the final biocrude. Indeed, biocrude is soluble in all solvents, and char is not formed by degradation of biocrude but rather by degradation of early carbohydrate intermediates. Effective solvents show a good affinity with the biomass, e.g., as expressed by Hildebrand values of 25−40 MPa 1/2 or small Hansen distances (Ra) to cellulose and lignin. Protic solvents further slowed the liquefaction reaction.

Abstract. Using the method of Guibe et al. we were able to selectively introduce an allyl group at the 2-position in methyl-4,6-O-(tetraisopropyldisiloxane-l,3-diyl)-a-~-glucopyranoside and benzyl--4,6-O-(tetra~sopropyldisiloxane-1,3-d~yl)-~-~-glucopyranoside. The dynamic properties of the tetraisopropyldisiloxane-l,3-diyl protective group gave us access to a glucose derivative which carried a I-propenyl group at the 2-position, an allyl group at the 6-position and a tetraisopropyldisiloxane-l,3-diyl at the 3,4-position together with a glucose derivative protected with an allyl, an acetyl and a 3-hydroxytetraisopropyldisiloxanyl at the 2-, 3-and 4-positions, respectively.

Phosphorylierung des Thymidins (Ia) bzw. des Diacylglycerins (Va) mit dem Reagenz (II) gibt die Derivate (Ib) bzw. (Vb), die unmittelbar mit dem Alkohol (III) bzw. mit (Ia) umgesetzt werden.

Abstract. The preparation of two diphosphorylated Lipid A analogues, which contain a-or P-phosphates at the reducing end, is described (i.e. compounds 14d and 15d, respectively). The synthesis of these compounds was accomplished using: (i) two suitably protected glucosamine derivatives, i.e. the non-reducing part 6 and the reducing part 3; (ii) an iridium catalyst to isomerize the anomeric ally1 ethers quantitatively into 1-propenyl ethers, which can then be removed to give simultaneously oxazoline functions (i.e. isomerization of 4b into 5 and of 7a into 7b); (iii) the levulinoyl* group for temporary protection of the 4-hydroxyl group; (iu) l-hydroxybenzotriazole--activated phosphorylating agents for the phosphorylation of the 4'-hydroxyl group (i.e. phosphorylation of compound 8 to give 10a,b); ( u ) 2,2,2-tribromoethyl phosphate for the phosphorylation of the reducing anomeric centre of Lipid A analogues (i.e. phosphorylation of lla,b to afford 13a,b). Non-reducing part 6 and reducing part 3 were reacted together to give the disaccharide 7a, which was converted into non-phosphorylated Lipid A precursor 8. Phosphorylation of compound 8 at its 4'-hydroxyl function and at its reducing anomeric centre resulted in the formation of fully protected a-phosphorylated Lipid A analogues 14a and 14b together with the fully protected P-phosphorylated analogues 15a and 15b. Final removal of all the protecting groups from 14a,b and 15a,b gave the a-phosphorylated Lipid A analogue 14d and the P-phosphorylated Lipid A analogue 15d, respectively.