Proton and Carbon‐13 NMR Studies of Some Tryptamines,Precursors, and Derivatives: Ab Initio Calculations for Optimized Structures

Abstract

Proton and carbon‐13 NMR data are presented for 5‐methoxytryptamine, 1; 6‐methoxytryptamine, 2; N,N‐diisopropyl‐5‐methoxytryptamine, 3, (5‐MeO‐DIPT); and N,N‐diisopropyl‐5‐methoxyindole‐3‐glyoxylamide, 4, at 300 MHz (¹H) and 75 MHz (¹³C) in CDCl₃ at ambient temperature. Compound 3, considered a potential hallucinogen, had been placed into Schedule I of the Controlled Substances Act, effective April 4, 2003, by the U.S. Drug Enforcement Administration. Compound 4 can serve as a possible precursor to 3. We believe that these are the first proton NMR assignments obtained at medium field (7 tesla) using selective homodecoupling and two‐dimensional homonuclear chemical shift correlation spectra (using one or more of the COSY45, COSY90, and COSYLR experiments) for rigorous aryl proton assignments in this group of compounds. Significant observed differences in the proton and carbon‐13 NMR spectra should allow facile distinction of the 5‐methoxy series, 1 and 3, from the 6‐methoxy series, 2. Energy minimizations to obtain optimized structures for each compound were performed at the Hartree–Fock level with the 6‐31G* basis set, and the resulting geometries are discussed. The presented geometry calculations appear to be the most accurate reported to date for 1 based on the basis set employed, and the first HF/6‐31G* structures for compounds 2, 3, or 4. Appreciable geometry differences in 3 and 4 for the pendant sidechain containing the N[CH(CH₃)₂]₂ moiety are noteworthy. Proximity of the carbonyl oxygens in 4 to H2 and H4 is suggested as a possible contributing factor in the deshielding of these protons in the NMR spectrum.     

XFEL experiments: jitter of pump–probe time delays and pulse intensities

Jitter of XFEL signals due to fluctuations in shot‐to‐shot time delays and intensities are explored in the frame of a statistical theory of X‐ray diffraction from liquids. Deformed signals are calculated at different levels of pump–probe jitter. A new method is proposed to eliminate these distortions.     

Diffractive–refractive optics: X‐ray splitter

The possibility of splitting a thin (e.g. undulator) X‐ray beam based on diffraction–refraction effects is discussed. The beam is diffracted from a crystal whose diffracting surface has the shape of a roof with the ridge lying in the plane of diffraction. The crystal is cut asymmetrically. One half of the beam impinges on the left‐hand part of the roof and the other half impinges on the right‐hand side of the roof. Owing to refraction the left part of the beam is deviated to the left whereas the right part is deviated to the right. The device proposed consists of two channel‐cut crystals with roof‐like diffraction surfaces; the crystals are set in a dispersive position. The separation of the beams after splitting is calculated at a distance of 10 m from the crystals for various asymmetry and inclination angles. It is shown that such a splitting may be utilized for long beamlines. Advantages and disadvantages of this method are discussed.     

Steric effect in alkylation reactions by N‐alkyl‐N‐nitrosoureas: a kinetic approach

The alkylation reactions of 4‐(p‐nitrobenzyl)pyridine (NBP), a trap for alkylating agents with nucleophilic characteristics similar to DNA bases, by five N‐alkyl‐N‐nitrosoureas (methyl‐, ethyl‐, propyl‐, butyl‐, and allylnitrosourea) were investigated in 7:3 (v/v) water/dioxane medium in the 5.0–6.5 pH range. Decomposition of alkylnitrosoureas (ANU) gives rise to alkyldiazonium ions that yield NBP‐R adducts directly or through carbocations in certain instances. The NBP alkylation rate constants by these species were determined. The following sequence of alkylating potential was found: methyl‐ > ethyl‐ > allyl‐ > propyl‐ > butyl group. Application of Ingold–Taft correlation analysis to the kinetic results revealed that the NBP alkylation reactions occur mainly through steric control. The values of the molar absorption coefficients of the NBP‐R adducts also reveal the determinant influence of a steric effect in the formation of alkylation adducts. The kinetic results are consistent with the biological activity of ANU. Copyright © 2008 John Wiley & Sons, Ltd.     

Collision processes of Hydride species in Hydrogen plasmas: III. The Silane family

Cross sections are provided for most important collision processes of the Silicon‐Hydrides from the “Silanefamily”: SiH_y (y = 1 ? 4) molecules and their ions SiH⁺_y, with (plasma) electrons and protons. The processes include: electron impact ionization and dissociation of SiH_y, dissociative excitation, ionization and recombination of SiH⁺_y ions with electrons, and charge ‐ and atom ‐ exchange in proton collisions with SiH_y. All important channels of dissociative processes are considered. Information is also provided on the energetics (reactants/products energy loss / gain) of each individual reaction channel. Total and partial cross sections are presented in compact analytic forms. The critical assessment of data, derivation of new data and presentation of results follow closely the concepts of the recently published related databases for Carbon‐Hydrides, namely for the Methane family [1, 2], and for the Ethane‐ and the Propane families [3], respectively. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Beamline BL‐07 at Indus‐2: a facility for microfabrication research

The X‐ray lithography beamline on Indus‐2 is now operational, with two modes of operation. With a pair of X‐ray mirrors it is possible to tune the energy spectrum between 1 and 20 keV with a controlled spectral bandwidth. In its `no optics' mode, hard X‐rays up to 40 keV are available. Features and performance of the beamline are presented along with some example structures. Structures fabricated include honeycomb structures in PMMA using a stainless steel stencil mask and a compound refractive X‐ray lens using a polyimide–gold mask in SU‐8.