Studies on the total syntheses of ß­carboline alkaloids orthoscuticellines A and B.

Orthoscuticellines A and B are newly isolated natural ß-carboline alkaloids from the moss animal Orthoscuticella ventricosa. Herein, we report the first targeted total synthesis of orthoscuticelline B and an analogous synthetic method for the preparation of dihydro derivate of orthoscuticelline A. The new synthetic approach is based on commercially available and inexpensive reagents leading to a practical synthesis of the target molecules. The reaction sequence consisting of a T3P®-catalyzed amide formation followed by a Bischler-Napieralski cyclisation and a DDQ-assisted dehydrogenation step ensures a practical access to orthoscuticelline B in three steps with 58% overall yield.

Segmented Contracted Error-Consistent Basis Sets of Quadruple-ζ Valence Quality for One- and Two-Component Relativistic All-Electron Calculations.

Segmented contracted basis sets of quadruple-ζ quality for exact two-component (X2C) calculations are presented for the elements H-Rn. These sets are the all-electron relativistic counterparts of the Karlsruhe "def2" and "dhf" systems of bases, which were designed for Hartree-Fock and density functional treatments and-with a somewhat extended set-also for correlated treatments. The bases were optimized with analytical basis set gradients and the finite nucleus model based on a Gaussian charge distribution at the scalar-relativistic X2C level. Extensions are provided for self-consistent two-component treatments to describe spin-orbit coupling, polarization effects, and nuclear magnetic resonance (NMR) shielding constants. The basis sets were designed to yield comparable errors in atomization energies, orbital energies, dipole moments, and NMR shielding constants all across the periodic table of elements. A test set of more than 360 molecules representing (nearly) all elements in their common oxidation states was utilized for the valence properties, and a test set of more than 250 closed-shell molecules was employed for the NMR shielding constants. The quality of the developed basis sets is compared to other frequently used relativistic all-electron bases.

Segmented Contracted Error-Consistent Basis Sets of Double- and Triple-ζ Valence Quality for One- and Two-Component Relativistic All-Electron Calculations.

Segmented contracted Gaussian basis sets optimized at the one-electron exact two-component (X2C) level - including a finite size model for the nucleus - are presented for elements up to Rn. These basis sets are counterparts for relativistic all-electron calculations to the Karlsruhe "def2" basis sets for nonrelativistic (H-Kr) or effective core potential based (Rb-Rn) treatments. For maximum consistency, the bases presented here were obtained from the latter by modification and reoptimization. Additionally we present extensions for self-consistent two-component calculations, required for the splitting of inner shells by spin-orbit coupling, and auxiliary basis sets for fitting the Coulomb part of the Fock matrix. Emphasis was put both on the accuracy of energies of atomic orbitals and on the accuracy of molecular properties. A large set of more than 300 molecules representing (nearly) all elements in their common oxidation states was used to assess the quality of the bases all across the periodic table.

The chemical space of PbN-nBin and (PbN-nBin)+: A systematic study for N = 3-13.

A systematic exploration of the energy hypersurfaces of three to 13-atomic neutral and cationic binary lead-bismuth clusters is presented. Global minima for all 99 compositions (N = 3-13, n = 0-N) were obtained by a density functional theory based genetic algorithm, which was applied to every single composition, both for the neutral clusters and for the cations. Within the genetic algorithm, the energetically most favorable assignment of atom types to atom positions was found via aimed swapping of element types, based on first-order perturbation theory in the nuclear charge. Results of the genetic algorithm procedure were refined with high-level density functional treatments including also the effects of spin-orbit coupling. The resulting global minima were analyzed applying various stability criteria, finally yielding the ∼20 overall most stable neutral and cationic clusters in the chemical space of three to 13-atomic mixed lead bismuth clusters. In most cases, they are polyhedrons that obey the Wade-Mingos rules.

Ionic-radius-driven selection of the main-group-metal cage for intermetalloid clusters [Ln@Pbx Bi14-x](q-) and [Ln@Pby Bi13-y](q-) (x/q=7/4, 6/3; y/q=4/4, 3/3).

Reactions of the binary, pseudo-homoatomic Zintl anion (Pb2 Bi2 )(2-) with Ln(C5 Me4 H)3 (Ln=La, Ce, Nd, Gd, Sm, Tb) in the presence of [2.2.2]crypt in ethane-1,2-diamine/toluene yielded ten [K([2.2.2]crypt)](+) salts of lanthanide-doped semimetal clusters with 13 or 14 surface atoms. Single-crystal X-ray diffraction and energy-dispersive X-ray spectroscopy indicated the presence of the anions [Ln@Pb6 Bi8 ](3-), [Ln@Pb3 Bi10 ](3-), [Ln@Pb7 Bi7 ](4-), or [Ln@Pb4 Bi9 ](4-) in single or double salts; the latter showed various ratios of the components in the solid state. The anions are the first ternary intermetalloid clusters comprising only elements of the sixth period of the periodic table, namely, Pb, Bi and lanthanides. This study, which was complemented by ESI mass spectrometry and (139) La NMR spectroscopy in solution, rationalizes a continuous development of the ratio of 13:14-atom cages with the ionic radius of the embedded Ln(3+) ion, which seems to select the most suitable cage type. Quantum chemical investigations helped to analyze this situation in more detail and to explain the observed subtle influence of the atomic radii. Magnetic measurements confirmed that the embedded Ln(3+) ions keep their expected paramagnetic or diamagnetic nature.

Error-Balanced Segmented Contracted Basis Sets of Double-ζ to Quadruple-ζ Valence Quality for the Lanthanides.

For lanthanides, segmented contracted Gaussian basis sets of double-ζ valence to quadruple-ζ valence quality are presented, with two different polarization sets for each level of quality. The bases are designed for use in connection with small-core Wood-Boring effective core potentials. A set of compounds representing most lanthanides in their common oxidation states is used to assess the quality. Parameters investigated were atomization energies, dipole moments, and structure parameters for Hartree-Fock, density functional, and correlated (Møller-Plesset) methods. So, the "def2" basis set series is extended to lanthanides with errors that are very similar to those previously obtained for the other elements with this type of basis set. Furthermore, for lanthanides, auxiliary bases for density fitting of Coulomb and Hartree-Fock exchange matrices are presented and tested.