Reactions of stereocontrolled intramolecular carbocyclization of levoglucosenone adduct with isoprene

An intramolecular carbocyclization was found of levoglucosenone adduct with isoprene providing a fused cyclobutane. The intramolecular oxacyclization of the adduct was performed under the treatment with I₂, H₃PO₄, SOCl₂, and Pd/C leading to 1,4-epoxide. Methods were developed of radical and anionic (by Ferrier method) transformation of the adduct into chiral trans- and cis-decalins.     

Unusual regioselectivity in a Diels-Alder reaction of isoprene with levoglucosenone

The ZnCl₂-catalyzed [4+2]-cycloaddition of isoprene with levoglucosenone is highly regio- and stereoselective.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 2047–2049, August, 1996.     

Stereochemical differentiation in the reactions of organometallic reagents with levoglucosenone and some of its dihydro derivatives

The reactions of methylmanganese iodide with levoglucosenone, its dihydro derivative, and 1.6-anhydro-3-deoxy-4-O-methyl-β-d-erythro-hexopyran-2-ulose were found to be highly diastereoselective compared to the reactions of Li-, Mg-, and Cu-based reagents. This specific feature of the manganese reagent is due to the enhanced tendency of manganese for chelation. Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1240–1243, July, 2000.     

Cross-aldol reactions of levoglucosenone and its derivatives with cyclohex-1-en-1-ol ethers

The reaction of levoglucosenone with cyclohex-1-en-1-yl trimethylsilyl ether under Mukaiyama reaction conditions gave [1 + 2]-Michael–aldol condensation product with participation of the acetal center. The reaction was accompanied by opening of the 1,6-anhydro bridge and intramolecular hemiketalization by the hydroxy group of the 2-oxocyclohex-1-enyl fragment. Under analogous conditions, dihydrolevoglucosenone gave rise to four diastereoisomeric 1,2-addition products. Internal cyclohex-1-en-1-ol ether obtained by treatment of the Michael adduct of levoglucosenone and cyclohexanone with Ac₂O–ZnCl₂ underwent intramolecular Mukaiyama reaction involving substituted α-carbon atom of the cyclohexanone fragment and acetal moiety to afford spiro derivative and product of subsequent AdE1 acetylation of intermediate α′-cyclohexenyl ether fragment.     

Eleuthesides and their analogs: I. Synthesis of the base compound from levoglucosenone adduct with piperylene

The Diels-Alder adduct of levoglucosenone and piperylene was converted into the corresponding oxime, and second-order Beckmann rearrangement of the latter, followed by treatment with a base, gave (1S,2R,6R)-6-(2-hydroxyethyl)-2-methylcyclohex-3-ene-1-carbaldehyde which was used in the synthesis of eleutheside analog. Conditions were found for opening of oxirane ring with formation of primary alcohol and simultaneous reduction of cyano group to aldehyde by the action of Red-Al-H₂O.     

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.     

Ferric chloride: a mild and versatile reagent for the formation of 1,6-anhydro glucopyranoses

A novel method for the preparation of 1,6-anhydro glucopyranoses (mono- and disaccharides) utilizing anhydrous FeCl₃ as Lewis acid is described. Treatment of methyl 6-O-benzyl and 6-O-p-methoxybenzyl-α/β d-glucopyranosides derivatives with FeCl₃ in CH₂Cl₂ at room temperature and 40°C afforded 1,6-anhydro glucopyranosides in moderate to good yields, through a debenzylation and intramolecular glycosidation in one step. A plausible reaction pathway is proposed.     

Synthesis of 20-hydroxyecdysone oxime, its diacetonide, and their 14,15-anhydro derivatives

20-Hydroxyecdysone oxime, its diacetonide, and the corresponding 14,15-anhydro derivatives were synthesized. Conditions were found for the preparation of the Z-and E-oximes, and their characteristics ¹H and ¹³C NMR parameters were determined.     

Synthesis and fungicidal activity of methylsulfanylmethyl ether derivatives of levoglucosenone

Chemistry of Heterocyclic Compounds - A series of derivatives were synthesized on the basis of levoglucosenone that contained hydroxy groups at the С-4 atom or С-2 and С-4 atoms...     

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.     

Copolymerization of 1,6-anhydroglucose and 1,6-anhydromaltose derivatives

The copolymerization of 1,6-anhydro-2,3,4-tri-O-(p-methyl-benzyl)-β-D -glucopyrnose [TXGL, M₁] with 1,6-anhydro-2,3-di-O-benzyl-4-O-(2,3,4,6-tetra-O-benzyl-α-D -glucopyranosyl)-β-D -glucopyranose [HBMA, M₂] has been studied as a method of producing dextrans of controlled composition with a linear backbone and randomly distributed single glucose units as side chains. Copolymers of intrinsic viscosities ranging from 0.51 to 0.05 dl/g are produced. The copolymerization appears to follow classical copolymerization theory but is affected adversely by the low reactivity of the maltose derivative. Reactivity ratios have been calculated for runs catalyzed by 10 mole-% and 20 mole-% phosphorus pentafluoride (PF₅): r₁ = 1.91 ± 0.35, r₂ = 0.28 ± 0.25 and r₁ = 2.21 ± 0.15, r₂ = 0.21 ± 0.10, respectively.     

单萜/顺丁烯二酸酐加成物及其酯类衍生物的气相色谱法分析

 摘要：研究了单萜/顺酐加成物及其酯化衍生物在OV-17和SE-30柱上的某些色谱性能和定量分析的线性相应关系。结果表明,这两种化合物在涂渍量为5％～10％的OV-17和SE-30柱上均能正常出峰;在峰形对称性和出峰时间上,OV-17柱具有优势。260℃以后,色谱峰面积与汽化温度无关。     

Copolymerization of 1,6-anhydro-ß-D-galactopyranose and 1,6-anhydro-ß-D-mannopyranose derivatives

1,6-Anhydro-2,3,4-tri-O-(p-methylbenzyl)-ß-D -galactopyranose (TXGal,M₁) has been copolymerized with 1,6-anhydro-2,3,4-tri-O-benzyl-ß-D -mannopyranose (TBMan,M₂), the products characterized by NMR, specific rotation, and viscosity, and the reactivity ratios calculated. The reactivity ratios r₁ = 0.37 ± 0.15 and r₂ = 38 ± 4 indicate that the anhydromannose derivative is about 100 times as reactive as that of anhydrogalactose. A comparison of glucose, mannose, and galactose copolymerizations suggests that the reactivity differences of the three propagating cations are comparatively small and the reactivity differences of the monomers large. This result is consistent with a mechanism proposed earlier. Methyl substitution on the aromatic rings of the p-xylyl groups inhibits the initiation process significantly relative to benzyl, but propagation only slightly.     

Cyclization/acylation reactions by nickel-catalyzed reactions of 1,6-ynal and 1,6-enyne derivatives with acylzirconocene chloride

NiCl₂(PPh₃)₂-catalyzed reactions of 1,6-ynal or 1,6-enyne compounds with n-nonanoylzirconocene chloride afforded stereoselectively cyclopentane derivatives or bicyclo[3.1.0] compounds by catalytic cyclization/acylation reactions, which would involve (i) the primary formation of a metallacycle followed by (ii) the transfer of an acyl group from the acylzirconocene complex (transmetalation).     

1,2和1,3-缩水内醚糖衍生物的制备, 构象及其糖苷化反应

吡喃糖的1,2-及1,3-缩水内醚苄醚由相应的吡喃糖的C-2氧负离子(对1,3-缩水内醚是C-3氧负离子)与连有氯原子的C-1经分子内关环反应而制备, 而有些吡喃糖的1,2-缩水内醚苄醚是由相应的吡喃糖的C-1氧负离子与连有对甲苯磺酰氧基的C-2经分子内关环(倒关环)反应而得。呋喃糖的1,2-缩水内醚苄醚只能用倒关环法合成。1,2-(或1,3-)缩水内醚糖的开环反应通常给出1,2-反式连接(对1,3缩水内醚是1,3反式连接)的糖苷键。1,2-及1,3-缩水内醚糖的构象分析是通过^1H NMR测定及分子力学计算的方法而完成的。