Cinchona alkaloid/sulfinyl chloride combinations: enantioselective sulfinylating agents of alcohols

We report a novel approach to asymmetric sulfinylation reactions based on a cinchona alkaloid/sulfinyl chloride combination that acts as the first asymmetric sulfinylating agents of achiral alcohols. Both enantiomers of arenesulfinates are obtained with up to 99% ee. The significantly high enantioselectivity observed in this case could be explained by dynamic kinetic resolution.     

Reactions of 6-thiotheophylline with alkylating agents and epichlorohydrin: Isolation of S-alkylated 6-thiotheophylline and 7-(2,3-thioepoxypropyl)theophylline

Alkylation of 6-thiotheophylline ( 1 ) under the aprotic basic condition affords S-alkylated 6-thiotheophylline ( 3 ) together with an N⁷ -alkylated product 4 . There is a tendency that the more reactive the alkylating agents are, the higher the yields of S-alkylated products are. On the other hand, treatment of 6-thiotheophylline ( 1 ) with epichlorohydrin afforded an unexpected product, 7-(2,3-thioepoxypropyl)theophylline ( 6 ), neither an S-alkylated compound 3g nor an N⁷ -alkylated compound 4g . The chemical structure was determined by nmr spectroscopic analysis.     

Highly enantioselective reaction of alpha-selenoorganolithium compounds with chiral bis(oxazoline)s and preparation of enantioenriched benzylidencyclohexanes

The enantioselective reaction of alpha-seleno carbanions derived from bis(phenylseleno)acetal and bis(2-pyridylseleno)acetal in the presence of bis(oxazoline)s with various electrophiles gave products with high enantioselectivity. The enantioselective reaction of alpha-lithio benzyl 2-pyridyl selenide gave the products with stereochemistry reverse to that obtained in the reaction of alpha-lithio benzyl phenyl selenide. Mechanistic investigation suggests the enantiodetermination of these reactions at -78 degrees C depends on dynamic thermodynamic resolution. The enantioselective reaction was applied to the preparation of enantioenriched olefins and epoxide.     

Temperature effect in separation of fullerene by high-performance liquid chromatography

Summary The effect of column temperature, especially at low temperatures, on the separation of fullerenes on monomeric and polymeric octadecyl silica (ODS) bonded phases has been studied. Decreasing the column temperature induces an increase in selectivity. The best temperature for the separation of fullerenes was determined for both types of ODS phase with n-hexane eluent. The selectivity for higher fullerenes on monomeric phases becomes similar to that on polymeric phases to low temperature. It has been found that as the carbon content of monomeric phases is increased, the selectivity also becomes similar to polymeric phases.     

Prostaglandin chemistry—IV : Microbiological kinetic resolution and asymmetric hydrolysis of 3,5-diacetoxycyclopent-1-ene

A 1:1 mixture of cis- and trans-3,5-diacetoxycyclopent-1-ene (1) was asymmetrically hydrolysed by baker's yeast to give trans-3(R)-acetoxy-5(R)-hydroxycyclopent-1-ene (R-2a) and S-predominant 3,5-dihydroxycyclopent-1-ene (3) accompanied by trans-3(R),5(R)-diacetoxycyclopent-1-ene (R-1a).The optical activities on the products were found to be dependent on the difference of the enzymatic hydrolytic rate among cis-, trans(S,S)- and trans(R,R)-3,5-diacetoxycyclopent-1-ene.The asymmetric hydrolysis was also investigated on wheat germ lipase, citrus acetyl esterase, and the lipase prepared from Aspergillus niger.     

The synthesis of pyrazolo[3,4-d]pyridazines. Photochemical cyclization to pyrazolo[3,4-d]pyridazin-4(5H)-ones with subsequent functionalization

The synthesis of 1,3-disubstituted and 1,3,5-trisubstituted 1H-pyrazolo[3,4-d]pyridazin-4(5H)-ones is conveniently performed by photochemical cyclization. Functionalization of the former compounds leading to the formation of 1,4-disubstituted and 1,3,4-trisubstituted 1H-pyrazolo[3,4-d]pyridazines is smoothly effected through pertinent nucleophilic substitutions.     

Clerodane-type diterpenoids from the japanese liverwort Jungermannia infusca (Mitt.) Steph

Three new clerodane-type diterpenoids have been isolated from the Japanese liverwort Jungermannia infusca (Mitt.) Steph., together with previously known compounds, nine clerodane- and four labdane-type diterpenoids, and 5-tocopherol. The structures of the new compounds were confirmed by 2D NMR experiments and X-ray crystallographic analysis.     

Studies on julimycins—VI The structures of julichromes Q1·2, Q2·2, Q3·5, Q3·5, Q4·5, Q2·5 and Q5·5

Julichromes Q_1·2 and Q_2·2 are identified as the dehydration products of julimycin B-II. The structures of julichromes, which commonly have a new anthraquinonyl Q₅ unit, are confirmed by their preparation from known julichromes. The conversion reaction, Q₂ → Q₅, which involves an intra-molecular redox is probably concerned in the biosynthesis of this unit.     

Improvement of substrate conversion to molecular hydrogen by three-stage cultivation of a photosynthetic bacterium,Rhodovulum sulfidophilum

In photosynthetic bacteria, after transition to light-anaerobic and nitrogen-deficient conditions, hydrogen evolution starts with expression of nitrogenase activity. Until the expression of enough activity,Rhodovulum sulfidophilum consumed substrates and converted them to poly(3-hydrox-ybutyrate) (PHB), resulting in a decrease in the proportion of substrate converted into hydrogen gas. To prevent conversion to PHB during the period when nitrogenase activity is derepressed, the authors employed a cultivation method consisting of three stages: cell growth, nitrogenase derepression, and hydrogen production. Cells cultivated by this method exhibited no lag time before the commencement of hydrogen evolution and gave an improved yield of hydrogen from the algal fermentative products.     

Polymerized Complex Route to the Synthesis of Pure SrTiO3 at Reduced Temperatures: Implication for Formation of Sr-Ti Heterometallic Citric Acid Complex

Powders of SrTiO3 were prepared by the Pechini-type polymerized complex technique, wherein a mixed solution of citric acid (CA), ethylene glycol (EG), Sr and Ti ions with a molar ratio of CA/EG/Sr/Ti = 10/40/1/1 was polymerized at 130°C to produce a yellowish transparent polyester-type resin without undergoing precipitation, which after decomposition on heating at 350°C was used as a powder precursor for SrTiO3. The formation of pure perovskite SrTiO3 practically free from carbonates occurred when the powder precursor was heat treated at temperatures higher than 500°C in static air. No X-ray diffraction and Raman spectroscopic evidence for phase separation of crystalline SrCO3 and TiO2 as distinct intermediates has been obtained during the thermal decomposition of the powder precursor, suggesting the molecular-scale mixing of cations in the Sr-Ti powder precursor. 13C-NMR spectroscopic measurements have indicated that unusual alkoxylation of CA occurred exclusively when both strontium and titanium ions in equal amounts coexist in CA/EG solutions, the phenomenon of which was discussed in connection with possible formation of a Sr-Ti heterometallic CA complex. The number of CA participating in formation of (Sr, Ti)-CAn was estimated to be n 3 from the variation of 13C-NMR spectra with relative concentrations of metal ions and CA. This heterometallic complex was thermally stable in CA/EG solutions upon heating at 130°C, implying that the molecular-level homogeneity achieved in the Sr/Ti precursor solution was preserved throughout the polymerization process.