Effect of γ-irradiation on the catalytic activity and selectivity of γ-alumina II. Conversion of isopropanol

The catalytic conversion of isopropanol was conducted over a poorly crystalline -alumina irradiated with different doses of -rays (25–150 Mrad). The catalytic reaction was carried out at 180–400°C in a flow technique under atmospheric pressure. The results showed that the dose of 25 Mrad resulted in a decrease of about 50% of the dehydration activity which suffered a further slight decrease upon irradiation at a dose of 50 Mrad. Increasing the dose in the range of 50–150 Mrad effected an increase in the dehydration activity reaching a maximum limit at 100 Mrad, then decreased abruptly by a dose of 150 Mrad. -irradiation led also to creation of some active sites contributing in dehydrogenation of isopropanol to producing acetone. These results were discussed in terms of removal of Brönsted acidity (25–50 Mrad), responsible for the dehydration reaction and to transformation of Lewis to Brönsted acidity (100 Mrad) by the action of liberated water from the dehydration reaction. The drop in dehydration activity due to irradiation at 150 Mrad might result from an efficient removal of the Brönsted acid sites created. The induced dehydrogenation activity of irradiated aluminas was attributed to creation of some electron-donor centers.     

Enzymatic lactonisation of γ-hydroxyesters in organic solvents. Synthesis of optically pure γ-methylbutyrolactones and γ-phenylbutyrolactone.

Porcine pancreatic lipase in anhydrous organic solvents catalyses the lactonisation of a number of esters of γ-hydroxyacids in nearly quantitative yields. This enzymatic process was used for the highly stereoselective synthesis of (S)-(−)-γ-methylbutyrolactone, (R)-(+)-γ-methylbutyrolactone and of optically active γ-phenylbutyrolactone.     

Synthesis of 4,4-dialkoxy-3-piperidinols. Application to the synthesis of γ-acetate dehydropipecolinonitrile

The synthesis of 4,4-dialkoxy-3-piperidinols 7 was carried out by the α-bromination of piperidin-4-one 5 with N-bromosuccinimide in acetic acid and alkoxide ion-mediated α,α-dialkoxyhydroxylation. Under acidic condition, trimethyl orthoformate-mediated reaction of compound 7a yielded aminodienylester 8 in the presence of Ph₃PCHCO₂Et. The γ-acetate dehydropipecolinonitrile 4 was also synthesized via boron trifluoride etherate-promoted addition of compound 8 with trimethylsilyl cyanide and N-bromosuccinimide and selective hydrogenation.     

Triterpenoids form species of Abies. XI. Ready fragmentation in the side chains of the molecules of triterpene α,β-unsaturated γ-keto acids

The structure of new trinortriterpene netural compounds formed as the result of the fragmentation of the side chains during the saponification of methyl esters of ,-unsaturated -keto acids under the action of alcoholic alkali have been established by physicochemical methods.Institute of Organic Chemistry, Siberian Branch, Academy of Sciences of the USSR, Novosibirsk. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 206–209, March–April, 1991.     

Nitroalkylation and nitroalkenylation reactions of γ-lactone enolates. A facile ring switch from polysubstituted γ-lactones to polysubstituted γ-lactams

Michael addition of lithium enolates of γ-butyrolactone 1 and α-methyl-γ-butyrolactone 1′ to (E)-1-nitropropene 2, (E)-β-nitrostyrene 3 and (E)-2-nitro-1-phenylpropene 4 is described. Reactions of the lithium enolate of 1′ with 2 and 4 occurred with high diasteroselectivity (80 and 92% d.e., respectively). Reactions of the zinc enolate of 1′ with two β-nitroenamines and two methylthio-substituted 1-amino-2-nitro-1,3-dienes were also examined. Catalytic reduction of the nitroalkylated and nitroalkenylated products allowed the achievement of functionalized γ-lactams and/or cyclic hydroxamic acids.     

Progress toward the synthesis of piperazimycin A: exploration of the synthesis of γ-hydroxy and γ-chloropiperazic acids

Employing Hamada’s chemistry with MAOS optimization of several steps, an expedient route to key (3S,5S)- and (3R,5R)-γ-hydroxy and (3R,5S)-γ-chloropiperazic acids, was developed en route to a total synthesis of piperazimycin A.     

New method for the synthesis of γ-diketones

Summary Over platinized charcoal at 300° 1-(2-furyl)-3-alkanols, as a result of the hydrogenolysis of the furan ring, and 1-(tetrahydro-2-furyl)-3-alkanols, as a result of the isomerization of the tetrahydrofuran ring, give-diketones in yields of 35–50%.     

Xylaropyrones B and C,new γ-pyrones from the endophytic fungus Xylaria sp. SC1440

Two new γ-pyrones, xylaropyrones B (1) and C (2), together with three known compounds, xylaropyrone (3), annularin A (4) and annularin C (5), were isolated from solid cultures of the endophytic fungus Xylaria sp. SC1440. The structures of these compounds were determined mainly by analysis of their NMR spectroscopic data. The relative configurations of 1 and 2 were assigned on the basis of J-based configurational analysis, and the absolute configurations were established by experimental and TDDFT calculated ECD spectra. The isolated compounds were evaluated for cytotoxic and tyrosinase inhibitory activity.     

Radiation-Induced,Solid-State Polymerization of Derivatives of Methacrylic Acid. XI. Aspects of the Polymerization of Methacrylic Acid by γ-Irradiation

Aspects of the radiation-induced polymerization of methacrylic acid in the crystalline state have been investigated and utilized to evaluate the mechanism of polymerization. In particular, results for post-irradiation polymerization at 0°C after radiation doses of 0.1 to 2.0 Mrad support the concepts of Lando and Semen that chain initiation essentially all commences at the same time, that chain propagation continues without termination, and that termination of nonpropagating radicals proceeds simultaneously.     

A synthesis of the γ-secretase inhibitor BMS-708163

A concise, convergent racemic synthesis of BMS-708163 is reported. Two fragments consisting of N-4-chlorophenylsulfonyl-3,3,3-trifluorpropylglycine and a 1,2,4-oxadiazole derivative of 2-fluorobenzyl alcohol were prepared in separate pots and then coupled together via a Mitsunobu reaction. Since a convenient chiral synthesis of optically pure (d)-3,3,3-trifluoropropyl glycine methyl ester was developed using Schöllkopf reagent alkylation, this methodology can also be adopted for the enantioselective synthesis of BMS-708163.     

Toward the synthesis of γ-pyrone-containing natural products: diastereoselective aldol-type reaction of a γ-pyrone

The diastereoselective aldol-type reaction of a γ-pyrone via a sodium anion has been developed. This reaction is useful for synthesizing γ-pyrone-containing natural products. Also, we applied the Mukaiyama aldol-type reaction of silyl enol ether of γ-pyrone by using TiCl₄. This Mukaiyama aldol-type reaction of γ-pyrone indicated higher anti-aldol selectivity than the aldol-type reaction of a γ-pyrone with NaHMDS.     

Radiation-Thermal Processes at the Surface of Pyrogenic γ-Alumina

The effects of ⁶⁰Co -radiation, 75-keV electrons, and thermal history (295–973 K) on the surface properties of pyrogenic -Al₂O₃ were studied by thermal desorption mass spectrometry. It was found that the state of a hydroxyl cover and the concentrations of surface acid–base sites and chlorine impurity atoms can be regulated by changing the conditions of oxide irradiation.     

Inclusional association as studied by the drying dissipative structure. Part 1. Drying patterns of α-, β- and γ-cyclodextrin

Macroscopic and microscopic drying patterns were observed on a cover glass, a watch glass, and a Petri glass dish during the course of dryness of aqueous solutions of α-cyclodextrin (αCD), β-cyclodextrin (βCD), and γ-cyclodextrin (γCD), i.e., cone shape oligomers of polysaccharide. For all CD molecules, two kinds of macroscopic patterns, outside and inner broad rings and spoke lines formed. Multi-broad rings were formed for βCD in the inner region of the main broad ring at the outside edge especially at the high concentrations. Cooperative drying processes of the convection, sedimentation, and solidification were clarified. Microscopic drying patterns showing the formation of rod-like and/or sward-like crystals were observed mainly in the direction along the spoke lines. The microscopic patterns of βCD were similar to those of some of polysaccharides and polynucleotides the authors studied previously. α- and γ-cyclodextrins were slightly hygroscopic, and clear-cut drying patterns were not observed.     

Intensity of the 1001 keV γ-ray in the decay of234mPa

The intensity of the 1001 keV -ray occurring in the decay of^234mPa in equilibrium with natural uranium sources is found to be (0.818±0.030)%. This value is in agreement with a recent measurement employing depleted uranium sources, but does not agree with earlier reports employing radiochemically pure sources.     

Reactions of γ-Sultines with Electrophilic Reagents. 2. Bromination of 3,5-Diaryl-1,2-oxathiolane 2-Oxides in the Presence of Lewis Acids

The bromination of 3,5-diaryl-1,2-oxathiolane 2-oxides (-sultines) has been studied in the presence of added Lewis acids. It was discovered that -sultines with donor substituents react with bromine with ring fission and conjugated addition of the nucleophilic reactant. Possible mechanisms for the reaction are discussed based on the data obtained.     

Microwave-promoted tandem reactions for the synthesis of bicyclic γ-lactams

A microwave-promoted three-step tandem process for the synthesis of bicyclic γ-lactams is developed. In all cases examined this led to significantly faster tandem processes producing the bicyclic γ-lactams more cleanly and reproducibly compared to standard thermal conditions.