Cross-sections of large-angle hadron production in proton- and pion-nucleus interactions I: beryllium nuclei and beam momenta of +8.9 GeV/c and −8.0 GeV/c

We report on double-differential inclusive cross-sections of the production of secondary protons, deuterons, and charged pions and kaons, in the interactions with a 5% λ _abs thick stationary beryllium target, of a +8.9 GeV/c proton and pion beam, and a −8.0 GeV/c pion beam. Results are given for secondary particles with production angles 20^○<θ<125^○. On leave of absence at Ecole Polytechnique Fédérale, Lausanne, Switzerland.     

Cross-sections of large-angle hadron production in proton– and pion–nucleus interactions VI: carbon nuclei and beam momenta from ±3 GeV/c to ±15 GeV/c

We report on double-differential inclusive cross-sections of the production of secondary protons, charged pions, and deuterons, in the interactions with a 5% λ _int thick stationary carbon target, of proton and pion beams with momentum from ±3 GeV/c to ±15 GeV/c. Results are given for secondary particles with production angles 20°<θ<125°. Cross-sections on carbon nuclei are compared with cross-sections on beryllium, copper, tantalum and lead nuclei.     

Cross-sections of large-angle hadron production in proton– and pion–nucleus interactions IV: copper nuclei and beam momenta from ±3 GeV/c to ±15 GeV/c

We report on double-differential inclusive cross-sections of the production of secondary protons, charged pions, and deuterons, in the interactions with a 5% λ _abs thick stationary copper target, of proton and pion beams with momentum from ±3 GeV/c to ±15 GeV/c. Results are given for secondary particles with production angles 20°<θ<125°. The inclusive pion production cross-sections are compared to those on beryllium and tantalum, published by us recently.     

Cross-sections of large-angle hadron production in proton– and pion–nucleus interactions VII: tin nuclei and beam momenta from ±3 GeV/c to ±15 GeV/c

We report on double-differential inclusive cross-sections of the production of secondary protons, charged pions, and deuterons, in the interactions with a 5% λ _int thick stationary tin target, of proton and pion beams with momentum from ±3 GeV/c to ±15 GeV/c. Results are given for secondary particles with production angles 20^○<θ<125^○. Cross-sections on tin nuclei are compared with cross-sections on beryllium, carbon, copper, tantalum and lead nuclei.     

A practical procedure for the removal of the phenylethanol moiety from phenylglycinol-derived lactams

Chiral non-racemic bicyclic lactams derived from phenylglycinol have been appointed as key building blocks for the preparation of enantiopure nitrogen compounds. The removal of the chiral inductor leading to substituted piperidones by using air or oxygen in basic media is presented.     

Toluene dioxygenase mediated oxidation of halogen-substituted benzoate esters

A series of ortho-, meta-, and para- halogen-substituted methyl benzoate esters was subjected to enzymatic dihydroxylation via the whole-cell fermentation with E. coli JM109 (pDTG601A). Only ortho-substituted benzoates were metabolized. Methyl 2-fluorobenzoate yielded one diol regioselectively whereas methyl 2-chloro-, methyl 2-bromo- and methyl 2-iodobenzoates each yielded a mixture of regioisomers. Absolute stereochemistry was determined for all new metabolites. Computational analysis of these results and a possible rationale for the regioselectivity of the enzymatic dihydroxylation is advanced.     

Enantioselective, protecting group-free synthesis of 1S-ethyl-4-substituted quinolizidines

A practical enantioselective protecting group-free four-step route to the key quinolizidinone 6 from phenylglycinol-derived bicyclic lactam 1 is reported. The Grignard addition reaction to 6 takes place stereoselectively to give 1-ethyl-4-substituted quinolizidines 4-epi-207I and 7-9. Following a similar synthetic sequence, 9a-epi-6 is also accessed. However, the addition of Grignard reagents to 9a-epi-6 proceeds in a non-stereoselective manner. In order to gain insight into the different stereochemical outcome in the two series, theoretical calculations on the iminium salts A and B have been performed. The study concludes that the addition of the hydride, which is the step that determines the configuration of the final products, occurs in a stereoelectronic controlled manner. The theoretical study is in agreement with the experimental results.     

Enzymatic metabolism of ergosterol by cytochrome p450scc to biologically active 17alpha,24-dihydroxyergosterol

We demonstrate the metabolism of ergosterol by cytochrome P450scc in either a reconstituted system or isolated adrenal mitochondria. The major reaction product was identified as 17alpha,24-dihydroxyergosterol. Purified P450scc also generated hydroxyergosterol as a minor product, which is probably an intermediate in the synthesis of 17alpha,24-dihydroxyergosterol. In contrast to cholesterol and 7-dehydrocholesterol, cleavage of the ergosterol side chain was not observed. NMR analysis clearly located one hydroxyl group to C24, with evidence that the second hydroxyl group is at C17. 17alpha,24-Dihydroxyergosterol inhibited cell proliferation of HaCaT keratinocytes and melanoma cells. Thus, in comparison with cholesterol and 7-dehydrocholesterol, the 24-methyl group and the C22-C23 double bond of ergosterol prevent side chain cleavage by P450scc and change the enzyme's hydroxylase activity from C22 and C20, to C24 and C17, generating bioactive product.     

Preparation of <Emphasis Type="Italic">α</Emphasis>-methyl-<Emphasis Type="Italic">γ</Emphasis>-butyrolactone: Mechanism of its formation and utilization in 2-methyl-1-tetralone synthesis

α-Methyl-γ-butyrolactone (III) has been prepared directly from γ-butyrolactone (I) in 89 % yield by selective monomethylation conditions: K₂CO₃/DMC/210°C/7 h. The reaction mechanism was elucidated and described. An intermediate and two byproducts: methyl tetrahydro-3-methyl-2-oxofuran-3-carboxylate (II), 3-(methoxycarbonyl)propyl methyl carbonate (IV) and 3-(methoxycarbonyl)butyl methyl carbonate (V) were identified. The high temperature disproportionation of K₂CO₃ in the presence of dimethyl carbonate to MeOK was observed. The new selective synthesis of 2-methyl-1-tetralone (VI) from α-methyl-γ-butyrolactone (III) by Friedel-Crafts conditions was performed in 79 % yield.