Monographie der Gattung Erythura Swainson, 1837 (Aves, Passeres, Estrilididae)

Volume: 2Start Page: 1End Page: 16

NMR spectroscopic and theoretical structural analysis of 5-benzyl substituted hydantoins in solution

The vicinal H,H and H,C coupling constants along the Ph-CH2AB-CRHM-C-X(=O)R' spin system of 5-benzyl substituted hydantoins together with the results of accompanying force field (TRIPOS) and quantum chemical ab initio calculations (GAUSSIAN-94 with atomic basis set of 3-21G type) were employed to report on the rotamer population about the hydantoin C(5)-benzyl substituent bond. The conformation having the phenyl ring folded over the hydantoin ring system proved to be preferred. (C) 1999 Elsevier Science B.V. All rights reserved

NMR spectroscopic and theoretical structural study of 5-exo-methylene-substituted hydantoins

The H-1 and C-13 NMR spectra of a series of 3-phenyl-5-exo-methylene-substituted hydantoins were recorded and assigned unequivocally by the various methods of 1D and 2D NMR spectroscopy. Employing the NMR parameters thus obtained, the NOEs between the different protons within the molecules and the results of accompanying semiempirical (AM1 and PM3, respectively) and ab initio (3-21G*) quantum chemical calculations, the tautomerism, the acidity, the redox potentials, the stereochemistry and the electron density distribution of the hydantoins were studied, In addition, the X-ray crystallographic structure of compound 1r is given and compared with the spectroscopic results

The influence of gene flow and drift on genetic and phenotypic divergence in two species of Zosterops in Vanuatu

Colonization of an archipelago sets the stage for adaptive radiation. However, some archipelagos are home to spectacular radiations, while others have much lower levels of diversification. The amount of gene flow among allopatric populations is one factor proposed to contribute to this variation. In island colonizing birds, selection for reduced dispersal ability is predicted to produce changing patterns of regional population genetic structure as gene flow-dominated systems give way to drift-mediated divergence. If this transition is important in facilitating phenotypic divergence, levels of genetic and phenotypic divergence should be associated. We consider population genetic structure and phenotypic divergence among two co-distributed, congeneric (Genus: Zosterops) bird species inhabiting the Vanuatu archipelago. The more recent colonist, Z. lateralis, exhibits genetic patterns consistent with a strong influence of distance-mediated gene flow. However, complex patterns of asymmetrical gene flow indicate variation in dispersal ability or inclination among populations. The endemic species, Z. flavifrons, shows only a partial transition towards a drift-mediated system, despite a long evolutionary history on the archipelago. We find no strong evidence that gene flow constrains phenotypic divergence in either species, suggesting that levels of inter-island gene flow do not explain the absence of a radiation across this archipelago