Synthesis of Some Neodihydrothebaine and Bractazonine Isomers

Theuns, Hubert G.; Lenting, H.B.M.; Salemink, C. A.; Tanaka, Hitoshi; Shibata, Masayoshi; Itô, Kazuo; Lousberg, R. J. J. C.

doi:10.3987/r-1984-09-1995

Cited by 12 publications

(24 citation statements)

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“…As shown in Figs 6 and 9, the break-point in dn/dz may occur at redshifts as low as z ∼ 1, and very likely z < 1.5, rather than z ∼ 1.7-2 as suggested by Theuns et al (1998) and Davé et al (1999). This shows that the UV background does not decrease as rapidly as the QSO-dominated UV background by Haardt & Madau (1996) used in simulations, and so galaxies could be a main source of the UV background at z < 2.5 and/or that the structure formation could be underestimated in simulations.…”

Section: The Evolutionary Behaviour Of Dn/dzmentioning

confidence: 69%

“…Alternatively, dn/dz could be almost constant for z < 2.5 with a large scatter from sightline to sightline. Theuns et al (1998) predict that dn/dz for the same column density range would show a non-evolution at z < 2. They do not, however, predict any spatial variation of dn/dz.…”

Section: The Evolution Of the Line Number Densitymentioning

confidence: 97%

“…Recently, from the study of the Lyα forest at 1.5 < z < 2.4, KCD conclude that the Lyα forest at 1.5 < z < 4 shows a monotonic, continuous evolution with z, in terms of the line number density, the mean H I opacity and the correlation strength, both from the profile fitting analysis and from the optical depth analysis. KCD also show that the change in the number density evolution occurs at z ∼ 1.2, suggesting that a QSO-dominated UV background used in numerical simulations underestimates the UV background and/or the enhanced structure formation at z < 2.5 (Theuns et al 1998;Weymann et al 1998;Davé et al 1999;Bianchi et al 2001). Therefore, it is of importance to investigate the redshift range where dn/dz starts to change and to study any variations from sightline to sightline from larger statistical sample in order to constrain the results from numerical simulations and the nature of the ionizing sources.…”

mentioning

confidence: 95%

“…These results suggest that the transition between the two different evolutionary rates occur somewhere in the range z ∼ 1.3 → 1.7. From numerical simulations, Theuns et al (1998) and Davé et al (1999) have demonstrated that the change in the evolutionary slope occurs at z ∼ 1.7 owing to the decreasing UV background at z < 2, assuming a QSO-dominated background. Recently, from the study of the Lyα forest at 1.5 < z < 2.4, KCD conclude that the Lyα forest at 1.5 < z < 4 shows a monotonic, continuous evolution with z, in terms of the line number density, the mean H I opacity and the correlation strength, both from the profile fitting analysis and from the optical depth analysis.…”

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confidence: 99%

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The physical properties of the Lyα forest at

Kim

Carswell

Cristiani

et al. 2002

Monthly Notices of the Royal Astronomical Society

143

284

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Combining a new, increased data set of eight quasi‐stellar objects (QSOs) covering the Lyα forest at redshifts 1.5 < z < 3.6 from VLT/UVES observations with previously published results, we have investigated the properties of the Lyα forest at 1.5 < z <4. With the six QSOs covering the Lyα forest at 1.5 < z < 2.5, we have extended previous studies in this redshift range. In particular, we have concentrated on the evolution of the line number density and the clustering of the Lyα forest at z≤ 2.5, where the Lyα forest starts to show some inhomogeneity from sightline to sightline. We have fitted Voigt profiles to the Lyα absorption lines as in previous studies, and have, for two QSOs with zem∼ 2.4, fitted Lyα and higher order of Lyman lines down to 3050 Å simultaneously. This latter approach has been taken in order to study the Lyβ forest at z∼ 2.2 and the higher H i column density Lyα forest in the Lyβ forest region. For a given NH I range, the Lyα forest at 1.5 < z < 4 shows the monotonic evolution, which is governed mainly by the Hubble expansion at this redshift range. In general, the Lyα forest line number density (dn/dz) is best approximated with dn/dz= 6.1(1 +z)2.47 ± 0.18 for the H i column density NH I= 1013.64−17 cm−2 at 1.5 < z < 4. When the results at 0 < z < 1.5 from Hubble Space Telescope (HST) observations are combined, the slow‐down in the number density evolution occurs at z < 1.5. For higher column density clouds at NH i > 1014 cm−2, there is a variation in the line number density from sightline to sightline at z < 2.5. This variation is stronger for higher column density systems, probably due to more gravitationally evolved structures at lower z. The mean H i opacity is at 1.5 < z < 4. HST observations show evidence for slower evolution of at z < 1. For NH i= 1012.5–15 cm−2, the differential column density distribution function, f(NH i), can be best fitted by f(NH I∝NH i−β with β≈ 1.5 for 1.5 < z < 4. When combined with HST observations, the exponent β increases as z decreases at 0 < z < 4 for NH i= 1013–17 cm−2. The correlation strength of the step optical depth correlation function shows the strong evolution from 〈z〉= 3.3 to 〈z〉= 2.1, although there is a large scatter along different sightlines. The analyses of the Lyβ forest at z∼ 2.2 are, in general, in good agreement with those of the Lyα forest.

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Section: The Evolutionary Behaviour Of Dn/dzmentioning

confidence: 69%

Section: The Evolution Of the Line Number Densitymentioning

confidence: 97%

mentioning

confidence: 95%

mentioning

confidence: 99%

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The physical properties of the Lyα forest at

Kim

Carswell

Cristiani

et al. 2002

Monthly Notices of the Royal Astronomical Society

143

284

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“…Employing the dibenzazonine base (244) a novel synthesis of cw-15,16-dimethoxyerythrinan-3-one (246b) has been reported [212]. This reaction seems to represent a useful route for the synthesis of Erythrina alkaloids Total synthesis of dibenz[d,/]azonine alkaloid bractazonine [213], laurifonine and laurifine [214] have been described. The latter, when heated with 10 per cent sulphuric acid, underwent cyclization to give the erythrinane base (246a) as the sole product, and this was converted (by treatment with excess diazomethane) into the dimethoxy derivative (246b).…”

Section: -Demethoxyerythratidinonementioning

confidence: 99%