Structural corrections of photinides A,B and their novel derivatives

Stereochemistries of the C2C8 double bond in photinides A and B were corrected to be reversed forms. The present studies also revised their absolute configurations by comparing the CD spectra of the degradation product with the corresponding synthetic sample. Discosia sp. SH 125 produced novel derivatives photinides X and Y, of which stereochemistry was established by NMR and CD analyses as well as theoretical calculations of the CD spectra.     

Experimental derivation of Auger transition probabilities from X-ray excited Auger electron spectra in XPS

Auger transition probabilities were experimentally derived from dominant XAES and related XPS peaks observed in XPS spectra. Some values of derived probabilities were higher than 1, because of addition or subtraction of background signal from the XAES or/and XPS peak intensity. However, the probabilities obtained are recognized to be useful for practical quantification by XAES and AES.     

Charge‐transfer complexes of N‐methyl‐, N‐iso­propyl‐, N‐butyl‐ and N‐iso­butyl­carbazole with 3,5‐di­nitro­benzoic acid

In the title four compounds, C₁₃H₁₁N·C₇H₄N₂O₆, (I), C₁₅H₁₅N·C₇H₄N₂O₆, (II), C₁₆H₁₇N·C₇H₄N₂O₆, (III), and C₁₆H₁₇N·C₇H₄N₂O₆, (IV), the donor and acceptor mol­ecules are stacked alternately to form one‐dimensional columns. In (I), the N‐methyl group of the donor is nearly eclipsed with respect to one of the nitro groups of the neighboring acceptor in a column, whereas the N‐iso­propyl, N‐butyl and N‐iso­butyl groups are in anti positions with respect to one of the nitro groups of the neighboring acceptor in compounds (II)–(IV).     

1,3‐Propane­di­ammonium bis(3′‐nitro‐trans‐cinnamate) and trans‐1,2‐cyclo­hexane­di­ammonium bis(3′‐nitro‐trans‐cinnamate)

In the title two adducts, C₃H₁₂N₂²⁺·2C₉H₆NO₄^?, (I), and C₆H₁₆N₂²⁺·2C₉H₆NO₄^?, (II), hydrogen bonds between the di­ammonium and carboxyl­ate ions form a two‐dimensional network parallel to the ab plane in (I) and one‐dimensional chains along the c axis in (II). The cyclo­hexane­di­ammonium ion in (II) has a crystallographic twofold axis.     

The First Fully Planar C5‐Conformation of Homooligopeptides Prepared from a Chiral α‐Ethylated α,α‐Disubstituted Amino Acid: (S)‐Butylethylglycine (=(2S)‐2‐Amino‐2‐ethylhexanoic Acid)

An optically active α‐ethylated α,α‐disubstituted amino acid, (S)‐butylethylglycine (=(2S)‐2‐amino‐2‐ethylhexanoic acid; (S)‐Beg; (S)‐ 2 ), was prepared starting from butyl ethyl ketone ( 1 ) by the Strecker method and enzymatic kinetic resolution of the racemic amino acid. Homooligopeptides containing (S)‐Beg (up to hexapeptide) were synthesized by conventional solution methods. An ethyl ester was used for the protection at the C‐terminus, and a trifluoroacetyl group was used for the N‐terminus of the peptides. The structures of tri‐ and tetrapeptides 5 and 6 in the solid state were solved by X‐ray crystallographic analysis, and were shown to have a bent planar C₅‐conformation (tripeptide) and a fully planar C₅‐conformation (tetrapeptide) (see Figs. 1 and 2, resp.). The IR and ¹H‐NMR spectra of hexapeptide 8 revealed that the dominant conformation in CDCl₃ solution was also a fully planar C₅‐conformation. These results show for the first time that the preferred conformation of homopeptides containing a chiral α‐ethylated α,α‐disubstituted amino acid is a planar C₅‐conformation.     

Copolymerization of cyclic ketene N,O-acetals with phenylisothiocyanate via zwitterionic intermediates

The reaction of 3-methyl-2-methylene-1,3-oxazolidine ( 1a ) and phenylisothiocyanate (PhNCS) gives 3-methyl-2-(phenylthiocarbamoyl)methylene-1,3-oxazolidine ( 3 ) whereas that of 2-isopropylidene-3-methyl-1,3-oxazolidine ( 1b ) and PhNCS gives 1:1 alternating copolymers. It is assumed that the reaction of 1b and PhNCS forms a zwitterionic intermediate ( 2b ), followed by the successive combination of 2b to give 1:1 alternating copolymers 4 and/or 5 . Consequently, it was demonstrated that the copolymerization of 1b and PhNCS proceeds via a zwitterionic mechanism with complete ring-opening to afford the 1:1 alternating copolymer 5 .     

Syntheses and properties of dithia‐tetrahomodiaza‐calix[4]arenes bridged by cystine unit

Dithia‐tetrahomodiaza‐calix[4]arenes were synthesized by the cyclization reactions of bis(3‐(chloro‐methyl)‐2‐hydroxyphenyl)sulfide with cystine peptides in moderate yields. Conformational analysis of the macrocycles by using nmr spectroscopy reveled that the cyclophanes adopt a cone‐like form as a preferable conformation and the cystine bridge moiety is incorporated in the cavity. The calixarene analogs can extract transion metals such as Zn²⁺ and Cu²⁺ ions from an aqueous phase into chloroform.     

rac‐ and meso‐3,3′‐Bis(3,5‐di­methyl­phenyl)‐3H,3′H‐2,2′‐biindenyl­idene‐1,1′(2H,2′H)‐dione

In the rac isomer of the title compound, C₃₄H₂₈O₂, the two C—Ph_{di­methyl­phenyl} bond axes make an angle of 58.7 (1)°. There is no short contact between the two 3,5‐di­methyl­phenyl rings, although the dihedral angle between them is 4.93 (7)°. The meso isomer has a center of symmetry at the middle of the C=C bond, and the two C—Ph_{di­methyl­phenyl} bond axes are antiparallel to one another.     

Depolymerization and ionic conductivity of enzymatically deproteinized natural rubber having epoxy group

Preparation of liquid epoxidized natural rubber (ENR) was made by oxidative depolymerization of ENR in latex stage without loss of epoxy group. Epoxidation of fresh natural rubber latex, which was purified by deproteinization with proteolytic enzyme and surfactant, was carried out with freshly prepared peracetic acid. The glass transition temperature (T_g) and gel content of the rubbers increased after the epoxidation, both of which were dependent upon an amount of peracetic acid. The gel content was significantly reduced by oxidative depolymerization of the rubber with (NH₄)₂S₂O₈ in the presence of propanal. The resulting liquid epoxidized rubber (M_n≈10⁴) was found to have well-defined terminal groups, i.e. aldehyde groups and α-β unsaturated carbonyl groups. The novel rubber was applied to transport Li⁺ as an ionic conducting medium, that is, solid polymer electrolyte.     

Gelation in free-radical terpolymerization of poly(allyl methacrylate) crosslinked polymer nanosphere with allyl benzoate and vinyl benzoate

Microgel-like poly(allyl methacrylate) (PAMA nanosphere) was prepared by the emulsion polymerization of AMA as the reactive crosslinked polymer nanosphere with abundant pendant allyl groups. The terpolymerization of PAMA nanosphere with allyl benzoate (ABz) and vinyl benzoate (VBz) was conducted in bulk using benzoyl peroxide as initiator at 80 °C. The gelation depended on the feed ABz/VBz molar ratio since the molecular weights of resulting poly(ABz-co-VBz)s that act as the bridges increased with an increase in the mole fraction of VBz in the feed monomer. Beyond the gel point, the sol was rapidly incorporated into the gel and the increasing tendency of the gel fraction became steeper from 70 to 95 mol% of VBz as a reflection of increased chain length of bridge between PAMA nanospheres. Moreover, the swelling ratio became lower with increasing the mole percentage of VBz in the feed monomer. These results would support the preferential incorporation of PAMA nanosphere into the gel and the longer bridge can capture more nanospheres to give a much shrunken gel.