A novel heterocycle composed of calicene and cyclopropenone hydrazone units —3,8-bis(t-butylthio)-5,6-diazatetracyclo-[8,3,0,02,4,07,9]trideca-1,3,6,8,10,12-hexaene

The titled compound (3) is synthesized by the reaction of 1,2-bis(dithiocyclopropenylio)cyclopentadienide with hydrazine. The ¹H- and ¹³C-NMR spectra suggest significant contribution of a novel polarized structure (3B) compared with a peripheral 14π conjugation structure (3A). Reaction features of 3 are also examined.     

Synthetic studies on the seven- and eight-membered rings by the intramolecular Nozaki-Hiyama reaction of the allylic phosphates

Synthetic studies on the seven- and eight-membered rings by the intramolecular Nozaki-Hiyama reaction of the allylic phosphates are described. The yield greatly depends on the structure of substrate; however, some complex substrates afforded desired products in high to excellent yield.     

A new 3-(phenylseleno)allylic cation: its regioselective C-C bond formation reaction with nucleophiles

Highly useful C-C bond formation using 2-ethoxy-3-(phenylseleno)prop-2-enal acetal 2 was examined with various Lewis acids. The reaction of 2 with the silyl enol ether in the presence of BF(3)*Et2O, ZnBr2, or SnBr4 regioselectively provided (Z)-3,4-diethoxy-5-(phenylseleno)pent-4-enophenone 5a in high yields. On the other hand, the reaction with other Lewis acids such as EtAlCl2 or SnCl4 gave 5-(phenylseleno)- 6 or non-selenopentane-1,4-dione 7, respectively. Novel prop-2-enal acetals 2-4 and 13-15 reacted with various nucleophiles to give pent-4-enophenones 5a,b, 10a, 12, and 16-18, S-ethyl pent-4-enoate 5b, alkylated vinylic sulfide 10b, 3-pentenenitrile 5d, and 10c. A versatile pent-4-enophenone 5a could be converted to tetrahydrofuran 20 and penta-2,4-dienophenone 19, the Diels-Alder reactions of which with dienophiles gave the adducts 24 and 25.     

Preparation of new chiral building blocks: highly enantioselective reduction of prochiral 1,3-cycloalkanediones possessing a methyl group and a protected hydroxymethyl group at their C2 position with baker's yeast or CBS catalyst

Highly enantioselective reduction of five-, six-, seven-, and eight-membered prochiral 1,3-cycloalkanediones possessing a methyl group and a protected hydroxymethyl group at their C2 position with baker's yeast or CBS catalyst and a new efficient and general method for preparing the 1,3-cycloalkanediones have been developed. These baker's yeast mediated reductions were found to produce corresponding ketols with high optical purity (>99% ee) and high yield. All of the prepared ketols and their derivatives, chiral building blocks, have been fully characterized, and their absolute configurations have been determined. These compounds would be useful for the convergent synthesis of complex natural products.     

Synthesis, thermal properties, and biodegradability of propyl-etherified starch

High amylose corn starch (HACS) was etherified with 1-bromopropane in dimethyl sulfoxide. The structure of the products was characterized by infra-red and ¹H-NMR spectroscopy. The degree of substitution (DS) on glucose unit calculated from ¹H-NMR spectrum was varied from 0.9 to 2.7 by changing feed ratio of 1-bromopropane to HACS. Thermogravimetric analysis reveals that the etherified HACS has a higher decomposition temperature than unmodified HACS. Differential scanning calorimetry analysis reveals that the etherified starch has a clear glass transition temperature which decreased with increasing DS, and that no melting point is observed. This result demonstrates that the etherified HACS mainly consists of amorphous region. The biodegradation rate decreases with increasing degree of etherification.     

Determination of molecular mass of acidic polysaccharides by capillary electrophoresis

We developed a method for the determination of molecular mass of acidic polysaccharides based on their high-resolution separation by capillary electrophoresis. Polymers of N-acetylneuraminic acid (NeuAc) and polysulfated hyaluronic acid were separated into their molecular species up to 100 mono- and 20 disaccharide units, respectively. The relationship between the molecular mass of NeuAc-polymer and their electrophoretic mobilities showed good linearity, and was applied to the determination of molecular masses of larger NeuAc species unresolved by capillary electrophoresis under the same conditions. In the first step, the standard curve for the determination of molecular mass was constructed from the relationship between electrophoretic mobility and molecular mass. Subsequently, the mobility was extrapolated to the standard curve, and the molecular mass was calculated. Five different preparations of NeuAc polymers having different molecular masses showed smaller values than those determined by conventional chromatographic techniques. Further, molecular mass determined by the present method correlated with number-average molecular mass. The methodology presented here was applied to the determination of molecular mass of polysulfated hyaluronic acid. The data indicated that native hyaluronic acid was extensively degraded during sulfonation reaction.     

"Amphiphilic" Cleavage of gamma-Stannyl Ketones with ATPH/RLi: Application to Enone Fragmentation by the Conjugate Addition - Cleavage Sequence

The use of a combined Lewis acid/base system consisting of aluminum tris(2,6-diphenylphenoxide) (ATPH) and MeLi has allowed the electrophilically activated nucleophilic ("amphiphilic") cleavage of C(alpha)-C(beta) bonds in gamma-stannyl ketones. Through combination with the conjugate addition of alpha-stannyl carbanion to enone, this approach constitutes a novel two-step conjugate addition - cleavage sequence that leads to functionalized ketones (see reaction).     

Investigation of the novel mixed-mode stationary phase for capillary electrochromatography. II. Separation of amino acids and peptides on sulfonated naphthalimido-modified silyl silica gel

The potential of 3-(4-sulfo-1,8-naphthalimido)propyl-modified silyl silica gel (SNAIP) as a mixed-mode stationary phase for capillary electrochromatography (CEC) was investigated for the separation of charged analytes, taking four amino acids (tyrosine, phenylalanine, tryptophan, histidine) as model analytes. The elution process of these charged analytes in CEC with SNAIP was dominated by a combination of both electrophoretic process and chromatographic process involving hydrophobic as well as electrostatic interactions. In order to study the retention mechanism, the CEC retention factor k* and the velocity factor ke* were measured for the amino acids, which allowed the assessment of the respective contribution from the differential processes underlying the separation. Migration and retention could be mediated by changing various mobile phase compositions, including buffer pH, buffer concentration, and concentration of organic solvent. Based on the results obtained by separation of the amino acids, the separation of eight peptides (Gly-Val, Gly-Phe, Gly-Ile, Gly-His, Gly-Lys, Lys-Lys, Gly-Gly-Gly, Gly-Gly-His) was attempted. A good separation was achieved under an isocratic elution with a mobile phase consisting of 35 mM phosphate buffer (pH 3.8) and 40% methanol.     

Photochemical reactions. 148th communication. Photochemistry of acylsilanes: Preparation,photolyses, and thermolyses of α,β-unsaturated silyl ketones

The syntheses, photolyses, and thermolyses of the α,β-unsaturated silyl ketones (E/Z)-7, (E)- 8 , and (E)- 9 are described. On n,π*-excitation (λ > 347 mm), the aforementioned compounds undergo (E/Z)-isomerization followed by γ-H abstraction. The intermediate enols are trapped intermolecularly by siloxycarbenes leading to the dimeric acetals 27A + B, 30A + B , and 31A + B . In addition, the acylsilanes (E/Z)- 7 undergo photoisomerization by δ-H abstraction furnishing the acylsilanes 29A + B . Flash vacuum thermolyses (FVT) of (E/Z)- 7 , (E/Z)- 8 , and (E)- 9 give rise to intramolecular reactions of the siloxycarbene intermediates. Thus, FVT (520°) of (E)- and (Z)- 7 selectively leads to the enol silyl ethers 32 and (E)- 33 , respectively, arising from carbene insertion into an allylic C–-H bond. FVT of (E/Z)- 8 (560°) and (E)- 9 (600°) affords the trienol silyl ethers 34A + B and the cyclic silyl ethers 37A + B , respectively, which are formed by CH insertion of the siloxycarbenes. As further products of (E)- 8 and (E)- 9 , the bicyclic enol ethers 35 and 36 are formed, presumably via siloxycarbene addition to the cyclohexene C?C bond.     

Design of novel inorganic-organic hybrid materials based on iron-chloranilate mononuclear complexes: characteristics of hydrogen-bond-supported layers toward the intercalation of guests

Novel intercalation compounds constructed from the common two-dimensional hydrogen-bond-supported layers and functional guests [(H(0.5)phz)(2)[Fe(CA)(2)(H(2)O)(2)].2H(2)O](n)(1), ([Fe(Cp)(2)][Fe(CA)(2)(H(2)O)(2)])(n)(2), ([Fe(Cp*)(2)][Fe(CA)(2)(H(2)O)(2)])(n)(3), and [(TTF)(2)[Fe(CA)(2)(H(2)O)(2)]](n)(4) (H(2)CA = chloranilic acid, phz = phenazine, [Fe(Cp)(2)] = ferrocene, [Fe(Cp*)(2)] = decamethylferrocene, TTF = tetrathiafulvalene) are described. The guest cations are introduced between the ([Fe(CA)(2)(H(2)O)(2)](m-))(l) layers by electrostatic (1-4) and pi-pi stacking (3, 4) interactions. [Fe(Cp*)(2)](+) cations in 3 are stacked on each other making tilted columns which are included in the channel created by the chlorine atoms of CA(2-) dianions. TTF cations in 4 are stacked face to face with two types of S...S distances (type A; 3.579(3) A, and type B; 3.618(3) A) making a columnar structure. The TTF cations in the stacked column have a head-to-tail arrangement with respect to the iron-chloranilate layer. M?ssbauer spectroscopy suggests that [Fe(CA)(2)(H(2)O)(2)](m-) anion in 3 is consistent with high-spin (S = 5/2) iron(III) ions and [Fe(Cp*)(2)](+) in the low-spin (S = 1/2) iron(III) ions. In 4, M?ssbauer spectroscopy shows high-spin iron(II) ions (IS = 1.10 mm.s(-1) and QS = 1.66 mm.s(-1) at 297 K) and high-spin iron(III) ions (IS = 0.42 mm.s(-1) and QS = 1.27 mm.s(-1) at 297 K), suggesting that the anionic layer of iron-chloranilate has a valence-trapped mixed-valence state. At the temperature range of 77-300 K, the compounds 1, 2, and 3 are EPR silent, whereas the EPR spectrum of 4 shows two types of signals with g = 2.008 indicating the radical form of TTF.