A novel design of a levoglucosenone derived chiral auxiliary

A two-step general approach to a new chiral auxiliary starting from levoglucosenone is reported. The compound is obtained by a [4+2] cycloaddition reaction with anthracene followed by a diastereoselective reduction of the C-2 keto function in high overall yield. The auxiliary has been used as chiral template in an asymmetric Diels-Alder reaction of the corresponding acrylic ester derivative with cyclopentadiene and shown to be efficient for asymmetric induction.     

DFT calculations induced a regiochemical outcome revision of the Diels-Alder reaction between levoglucosenone and isoprene

An appealing inversion in the regiochemical outcome of Diels-Alder reactions between levoglucosenone (1) and its α-bromo derivative (5) with isoprene (2) was studied computationally. Based on different DFT calculations we concluded that both reactions should display the same regioselectivity. This result was further validated experimentally.     

Unprecedented Biodegradable Cellulose-Derived Polyesters with Pendant Citronellol Moieties: From Monomer Synthesis to Enzymatic Degradation

Levoglucosenone (LGO) is a cellulose-derived molecule that is present commercially on a multi-ton/year scale. Taking advantage of the α,β-conjugated ketone of LGO, a new citronellol-containing 5-membered lactone (HBO-citro) was synthesized through a one-pot two-step pathway involving oxa-Michael addition and Baeyer-Villiger oxidation. The solvent-free treatment of HBO-citro with NaBH₄ at room temperature led to the full reduction of the lactone moiety which gave a novel fully renewable triol monomer having a citronellol side chain (Triol-citro). Noticeably, by simply changing the reducing agent, temperature and reaction duration, the partial reduction of HBO-citro can be achieved to yield a mixture of 5- and 6-membered Lactol-citro molecules. Triol-citro was chosen to prepare functional renewable polyesters having citronellol pendant chains via polycondensation reactions with diacyl chlorides having different chain lengths. Good thermal stability (T_d5% up to 170 °C) and low glass transition temperatures (as low as −42 °C) were registered for the polyesters obtained. The polymers were then hydrolyzed using a commercial lipase from Thermomyces lanuginosus (Lipopan^® 50 BG) to assess their biodegradability. A higher degradation profile was found for the polyesters prepared using co-monomers (acyl chlorides) having longer chain lengths. This is likely due to the decreased steric hindrance around the ester bonds which allowed enhanced accessibility of the enzyme.     

New chiral 1,2-aminoalcohols derived from biomass and their application in diethyl zinc additions

A convenient procedure for the preparation of chiral 1,2-aminoalcohols starting from levoglucosenone, a biomass derivative, is described. The 1,2-aminoalcohols, bearing primary, secondary, and tertiary amino groups, were tested as chiral catalysts in the asymmetric addition of diethyl zinc to benzaldehyde.     

Understanding the pyrolysis of CCA-treated wood: Part II. Effect of phosphoric acid

The pyrolysis process of chromated copper arsenate-treated wood impregnated with phosphoric acid (2–6 wt.%) has been investigated using a Kugelrohr short-path distillation apparatus. The presence of phosphoric acid is shown to change the overall pyrolysis kinetics and yields of products resulting in a decrease in the amount of volatile products and an increase in the char formation. The yield of levoglucosan was found to decrease in the presence of relatively higher concentrations of phosphoric acid, while the yield of levoglucosenone increased. The pyrolysis of chromated copper arsenate-treated wood in the presence of phosphoric acid gave rise to 22% (on water-free tar basis) levoglucosenone. Such data demonstrates the potential for a new pathway toward the rational utilization of chromated copper arsenate-treated wood waste.     

Assessing the halogen effect in Diels-Alder reactions involving chiral α-halo enones. A combined experimental and DFT computational approach

An experimental and computational study was conducted to assess the effect of chlorine and bromine substitution in Diels-Alder reactions involving chiral α-halo enones as dienophiles. An important rate enhancement was observed in the case of acyclic dienes, while the use of cyclic dienes resulted in prolonged reaction times and lower yields. DFT calculations suggest that these reactions are governed by finely balanced geometric and electronic features at the TSs.     

Thiosugars VI: A Simple Stereoselective Approach to (1→3)-3-S-Thiodisaccharides from Levoglucosenone

Summary.  A new stereoselective synthesis of (1→3)-3-S-thiodisaccharides is described. Levoglucosenone-derived chiral building blocks produced by the selenium-mediated iodination at C-3 afforded 3-iodoketones in moderate yield. Iodine displacement with sulfur nucleophiles (1-thiols) resulted in 3-thiodisaccharides. Following reduction of the C-2 keto function constituted a new two-step general approach to these biologically important thiosugars. Received November 11, 2001. Accepted November 22, 2001     

Diastereoselective Weitz-Scheffer epoxidation of levoglucosenone for the synthesis of isolevoglucosenone and derivatives

High-yielding epoxidation conditions for the cellulose pyrolysis product (?)-levoglucosenone (LGO) and 3-aryl derivatives of LGO have been developed. The reaction of LGO with hydrogen peroxide/base is known to give a Baeyer-Villiger reaction, however, it was found that the reactions of LGO or derivatives with tert-butylhydroperoxide/base affords solely epoxides through the Weitz-Scheffer reaction. A critical parameter in the successful isolation of the epoxide from LGO was to avoid all contact with water or alcohols during the reaction and workup. The epoxide products were reacted under Wharton conditions affording allylic alcohols and subsequent oxidation led to isolevoglucosenone or 3-arylisolevoglucosenone derivatives. Previously unreported reactions on isolevoglucosenone were then investigated.     

Exploring structural effects of levoglucosenone derived chiral auxiliaries in asymmetric Diels-Alder cycloadditions

New chiral auxiliaries derived from levoglucosenone were developed in a simple and efficient way and evaluated as chiral inductors in asymmetric Diels-Alder reactions between the corresponding acrylate derivatives and cyclopentadiene. The results showed an important influence of the absolute configuration of the C(2) center of the auxiliary on the level of stereoinduction obtained.     

Diastereoselective sulfa-Michael reactions controlled by a biomass-derived chiral auxiliary

A family of chiral auxiliaries derived from the lignocellulosic biomass pyrolysis product levoglucosenone (LGO) has been screened in the sulfa-Michael reaction. When promoted by inorganic bases with potassium counterions, the auxiliary with geminal benzyl substituents showed diastereoselectivity up to 90:10 for a broad range of α,β-unsaturated esters.