Manganese(III)-mediated free-radical cyclization of acitve methylene compounds,alkenes and molecular oxygen. Syntheses of sulfur- and phosphorus-containing 1,2-dioxan-3-ols

The reactions of β-keto sulfoxide, β-keto sulfones, or β-keto phosphinate with 1,1-disubstituted ethenes in the presence of manganese(III) acetate and molecular oxygen yielded 4-phenylsulfinyl-, 4-phenylsulfonyl-, or 4-phosphinoyl-1,2-dioxan-3-ols 3 in moderate-to-good yields. m-Chloroperbenzoic acid oxidation of 4-phenylsulfinyl-1,2-dioxan-3-ols gave the corresponding 4-phenylsulfonyl derivatives. The temperature dependence of the reactions was observed and the stereochemistry of the 1,2-dioxan-3-ols are discussed.     

Novel approach for catalytic cyclopropanation of alkenes via (2-furyl)carbene complexes from 1-benzoyl-cis-1-buten-3-yne

The reaction of conjugated ene-yne-ketones 3 with a variety of alkenes in the presence of a catalytic amount of Cr(CO)(5)(THF) at room temperature gives (2-furyl)cyclopropanes in good yields. These cyclopropanation reactions proceed via (2-furyl)carbene-chromium intermediates 4 formed in situ from ene-yne-ketones 3. Late transition metals, such as [RuCl(2)(CO)(3)](2), [RhCl(cod)](2), PdCl(2), and PtCl(2), also catalyze effectively the cyclopropanation of styrene with 3.     

A PL homotopy for finding all the roots of a polynomial

This paper presents a constructive method which gives, for any polynomialF(Z) of the degreen, approximate values of all the roots ofF(Z).. The point of the method is on the use of a piecewise linear function (Z, t) which approximates a homotopyH(Z, t) betweenF(Z) and a polynomialG(Z) of the degreen withn known simple roots. It is shown that the set of solutions to (Z, t) = 0 includesn distinct paths,m of which converges to a root ofF(Z) if and only if the root has the multiplicitym. Starting from givenn roots ofG(Z), a complementary pivot algorithm generates thosen paths.This work was supported by grants from Management Science Development Foundation and Takeda Science Foundation.     

Reaction of oligomethylene di(3-oxobutanoate) with 1,1-disubstituted alkenes and molecular oxygen in the presence of manganese(II and/or IE) acetate

The reactions of 1,1-disubstituted ethenes with oligomethylene di(3-oxobutanoate) in the presence of manganese(II and/or III) acetate and atmospheric oxygen yielded an ω-(3-oxobutanoyloxy)alkyl 6,6-diaryl-3-hydroxy-3-methyl-1,2-dioxane-4-carboxylate, oligomethylene di(6,6-diaryl-3-hydroxy-3-methyl-1,2-dioxane-4-carboxylate)s, ω-hydroxyalkyl 6,6-diaryl-3-hydroxy-3-methyl-1,2-dioxane-4-carboxylates, an ω-(3-oxobutanoyloxy)alkyl 5,5-diaryl-2-methyl-4,5-dihydrofuran-3-carboxylate, oligomethylene di(5,5-diaryl-2-methyl-4,5-dihydrofuran-3-carboxylate)s, ω-hydroxyalkyl 5,5-diaryl-2-methyl-4,5-dihydrofuran-3-carboxylates, and an ohgomethylene diester bearing a substituted 1,2-dioxane ring and a substituted 4,5-dihydrofuran ring. The reaction of the 1,2-dioxan-3-ols with acid gave the corresponding compounds bearing furan rings. The reaction of 1,1,6,6-tetraaryl-1,5-hexadienes with oligomethylene di(3-oxobutanoate) in the presence of manganese(III) acetate yielded macrocyclic diesters bearing two 4,5-dihydrofuran rings.     

Synthesis of Linear Amphipathic Porphyrin Dimers and Trimers: An Approach to Bilayer Lipid Membrane Spanning Porphyrin Arrays

A modular building-block approach has been developed for the construction of linear amphipathic porphyrin arrays. The reaction of meso-(trifluoromethyl)dipyrromethane and an aldehyde under the conditions of the two-step room temperature porphyrin synthesis affords the trans-substituted porphyrin (13-56% yields). A similar reaction with two different aldehydes provides access to porphyrins bearing two different functional groups. An ethyne porphyrin and an iodo porphyrin (either free base or zinc) are selectively joined via Pd(0)-catalyzed coupling reactions, affording a linear array with porphyrins in defined metalation states. Coupling of a zinc-porphyrin bearing iodo and ester groups with a free base porphyrin bearing ethyne and ester groups yielded the zinc-free base porphyrin dimer. Coupling of a bis-ethyne porphyrin with a porphyrin bearing iodo and ester groups afforded the porphyrin trimer. Cleavage of the esters yielded the amphipathic porphyrin dimer and trimer arrays. The arrays with adjacent zinc and free base porphyrins undergo efficient electronic energy transfer. Both amphipathic porphyrin arrays have been incorporated into L-alpha-phosphatidylcholine vesicles. This versatile synthetic strategy provides access to a family of porphyrin arrays for studies of photophysical processes in supramolecular assemblies.     

Elastic modulus of the crystalline regions of chitin and chitosan

The elastic moduli E_l of the crystalline regions of α‐chitin and chitosan in the direction parallel to the chain axis were measured by X‐ray diffraction. The E_l values were 41 GPa for α‐chitin, and 65 GPa for chitosan, respectively, at 20°C. The contracted skeletons of α‐chitin and chitosan are the key factor for the low E_l values compared with that (138 GPa) of cellulose I. The E_l value of α‐chitin was constant at 41 GPa both at −190°C and 150°C, which indicates that the molecular chain of α‐chitin is stable against heat within the temperature and stress range studied. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1191–1196, 1999     

Elastic modulus of the crystalline regions of polyimide derived from poly(amic acid)–biphtalic dianhydride and p-phenylene diamine

The elastic modulus E_l of the crystalline regions in the direction parallel to the chain axis was measured by X-ray diffraction for polyimide derived from polyamic acid (biphthalic dianhydride and p-phenylene diamine). These specimens were cured by two different routes: curing at 200 °C, and at 400 °C for 1 h, respectively (2STEPS), and curing from 80 °C to 400 °C stepwise (nine steps) for 1 h at each step (STEPWISE). The E_l values of 54–169 GPa were obtained for the STEPWISE specimen and 80–178 GPa for the 2STEPS specimen, depending on the meridional reflection employed for measurement of the E_l value. A linear relationship between the E_l value and the fiber identity period was obtained from each meridional diffraction, such that the E_l value increased with an increase in the fiber identity period. The E_l value of the fully extended structure was estimated to be 210 GPa. These are considered to be due to the coexistence of polymorphs with different skeletal structures. The crystalline regions of the 2STEPS specimen seems to consist of a more extended skeleton than those of the STEPWISE specimen. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 3294–3301, 1999     

Reductive coupling of carbonyl compounds using lanthanum metal

We found that lanthanum metal was an excellent agent for the reduction of carbonyl compounds in the presence of a catalytic amount of iodine. When carbonyl compounds were treated with lanthanum metal in the presence of a catalytic amount of iodine, the reductive coupling of the carbonyl compounds proceeded efficiently to afford the corresponding vic‐diols in moderate to good yields. © 2000 John Wiley & Sons, Inc. Heteroatom Chem 11:81–85, 2000     

基于Chlamydocin骨架设计合成环肽类HDACi及其抗肿瘤活性

组蛋白去乙酰化酶(HDACs)通过催化各种底物蛋白包括组蛋白、转录因子、α-微管蛋白和核输入蛋白等的ε-赖氨酸残基乙酰化侧链的去乙酰化来影响细胞功能,抑制HDAC活性可以治疗表观遗传异常引起的癌症和其他慢性疾病.以HDAC抑制剂(HDACi) Chlamydocin为骨架设计合成一类新型抑制剂,将HDACi的结合区设计为二硫键结构、在环肽中苯丙氨酸的苯环不同位点引入甲基,合成4种不同序列的环肽类HDACi.考察HDACi体外抗肿瘤细胞(MCF-7,Hela和7721)活性,结果表明HDACi对三种肿瘤细胞系均显示良好的生长抑制作用,细胞形态都发生明显变化,其中对Hela细胞的毒性最高,IC50达到0.1 μmol/L.     

Pd(0)‐catalyzed polycondensation of methyl propargyl carbonate and bisphenols under stoichiometrically imbalanced conditions

We found that a novel Pd(0)‐catalyzed polycondensation of methyl propargyl carbonate ( 1 ) and bisphenol analogs 4 such as 4,4′‐dihydroxydiphenyl ether (4b ) proceeded successfully and gave polyethers 5 having exomethylene groups. The polycondensation was affected by the kind of bisphenol analogs used. The molar ratio of 1 and 4 also affected the polymerization behavior. Polyethers 5 with higher molecular weights were obtained by polymerization with 0.5 equiv of 4 toward 1 . The use of 1 equiv of 4 gave poor results. When 4,4′‐dihydroxybenzophenone ( 4d ) was employed as a nucleophile, benzenesulfonamide ( 13 ) was needed as an additive for obtaining the corresponding polyether with higher molecular weight. The Pd(0)‐catalyzed condensation of 1 and p‐hydroxyacetophenone was conducted as a model reaction. The desired compound and three by‐products were produced. Two of the by‐products were formed by reaction of 1 and methanol liberated from 1 . The other one appeared to be formed via hydrogenolysis. The formation of the by‐products suggested that some terminal reactions took place in the polycondensation of 1 and 4 . © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2250–2261, 2008