Asymmetric Construction of Alkaloids Employing a Key ω-Transaminase Cascade

An ω‐transaminase triggered intramolecular aza‐Michael reaction has been employed for the preparation of cyclic β‐enaminones in good yield and excellent enantio‐ and diastereoselectivity, starting from easily accessible prochiral ketoynones and commercially available enzymes. The powerful thermodynamic driving force associated with the spontaneous aza‐Michael reaction effectively displaces the transaminase reaction equilibrium towards product formation, using only two equivalents of isopropylamine. To demonstrate the potential of this methodology, we have combined this biocatalytic aza‐Michael step with annulation chemistry, affording unique stereo‐defined fused alkaloid architectures

Quantum Rings in Electromagnetic Fields

This is the author accepted manuscript. The final version is available from Springer via the DOI in this recordThis chapter is devoted to optical properties of so-called Aharonov-Bohm quantum rings (quantum rings pierced by a magnetic flux resulting in AharonovBohm oscillations of their electronic spectra) in external electromagnetic fields. It studies two problems. The first problem deals with a single-electron AharonovBohm quantum ring pierced by a magnetic flux and subjected to an in-plane (lateral) electric field. We predict magneto-oscillations of the ring electric dipole moment. These oscillations are accompanied by periodic changes in the selection rules for inter-level optical transitions in the ring allowing control of polarization properties of the associated terahertz radiation. The second problem treats a single-mode microcavity with an embedded Aharonov-Bohm quantum ring which is pierced by a magnetic flux and subjected to a lateral electric field. We show that external electric and magnetic fields provide additional means of control of the emission spectrum of the system. In particular, when the magnetic flux through the quantum ring is equal to a half-integer number of the magnetic flux quanta, a small change in the lateral electric field allows for tuning of the energy levels of the quantum ring into resonance with the microcavity mode, thus providing an efficient way to control the quantum ring-microcavity coupling strength. Emission spectra of the system are discussed for several combinations of the applied magnetic and electric fields

TERAHERTZ PULSED SPECTROSCOPY OF PHARMACEUTICAL MATERIALS

Author Institution: TeraView LimitedTerahertz pulsed spectroscopy (TPS) is a recently developed quick, simple, and versatile technique for analyzing the chemical composition and physical form of a wide range of solid, liquid, and gaseous materials. Portable TPS systems using room temperature sources and detectors can now readily access the 'terahertz gap' with broadband coverage from 50 GHz to 4 THz ($1.3 cm^{-1}$ to $133 cm^{-1}$. For the first time the unique properties of terahertz radiation can be readily exploited in spectroscopy and imaging. TPS accesses low energy transitions including large-amplitude torsional vibrations (intra-molecular), intermolecular interactions such as hydrogen bonding, molecular rotations, and phonon bands. For solids it is often uniquely sensitive to the amorphous/crystalline state, hydration or water content, and polymorphic form of the material. This has allowed us to present a detailed investigation of the polymorphs of the important drug compounds ranitidine hydrochloride and carbamazepine. Full exploitation of TPS requires new spectrum libraries for identifying materials, evaluation of chemometric algorithms for quantitative analysis, and technical developments including accessories for non-contact online sampling in real-time. Recent developments in TPS will be presented including examples from a database of terahertz absorbance spectra for common materials. The unique terahertz signatures of target chemicals are complemented by the highly transmissive properties of common packaging materials including many plastics, allowing new sampling strategies to be considered. Quantitative studies demonstrate how multivariate analysis of terahertz spectra with established spectroscopic software can yield valuable multi-component information about active ingredients and excipients in pharmaceutical raw materials and products