Scopine Isolated in the Gas Phase

Abstract

The rotational spectrum of the tropane alkaloid scopine has been detected by Fourier transform microwave spectroscopy in a pulsed supersonic jet. A non-conventional method for bringing the molecules intact into the gas phase was used, mixing scopine syrup with solid glycine powder and vaporizing the solid mixture with an UV ultrafast laser beam. Laser vaporization prevented the easy isomerization to scopoline previously observed when conventional heating. A single conformer was unambiguously observed in the supersonic jet, which corresponds to the energetically most stable species according to quantum chemistry calculations. Rotational and centrifugal distortion constants have been accurately determined. The spectrum reveals hyperfine splittings due to the combined effect of hindered rotation of the methyl group and the presence of a quadrupolar nucleus ( 14 N).This additional information allowed determining the angle of N-methyl inversion between the N-CH3 bond and the bicyclic C-N-C plane (135º), as well as the internal rotation barrier of the methyl group (6.24(1) kJ mol -1 ).

N‐Methyl Inversion and Accurate Equilibrium Structures in Alkaloids: Pseudopelletierine

“…The jet population ratio shows that the concentration of the axial conformer is approximately twice that of the equatorial conformer.T he resulting relative energy betweent he two configurations (2.3 kJ mol À1 ) satisfactorily agrees with the MP2 predictions. Ac omparison of nitrogen inversion is now possible in four different tropane alkaloids, including tropinone, [7] scopoline, [9] scopine, [10] and pseudopelletierine (Figure 4). Pseudopelletierine and its homolog tropinone show reversed conformational trends because the equatorial preference in tropinone is reversed upon addition of am ethylene group in pseudopelletierine.…”

“…Previous studies on tropane alkaloids suggested possible connections between axial/equatorial isomerism ( N ‐methyl inversion) and its biological role, so the nature, position, arrangement, and stereochemistry of substituents may have a crucial role in the bioactivity of these molecules. For these reasons, our previous studies (tropinone, scopoline, scopine, and tropinone⋅⋅⋅H 2 O) have addressed the conformational flexibility, substituent effects, N‐ methyl inversion, and role of hydration in tropane alkaloids. Herein, we compare the structural effects associated with the larger ring of pseudopelletierine and the presence of the carbonyl group.…”

Simultaneous quantification of tiotropium bromide impurities G + H in capsule formulation by LC-MS/MS

“…In the literature research, it is stated that this transformation occurs at a high temperature (90˚C). 18 The mechanism of conversion of Impurity G to Impurity H is given in Figure 9. Therefore, the finished product containing tiotropium was considered to decompose to Impurity G in acidic or alkaline decomposition conditions.…”

Laboratory Observation of, Astrochemical Search for, and Structure of Elusive Erythrulose in the Interstellar Medium

“…To solve this problem, we decided to use the ultrafast laser vaporization technique as in the earlier studies of 5 C and 6 C sugars. ,− However, the production of the solid rods required for this approach was not straightforward since the compound was a viscous syrup. Neither were the alternative methods described in the literature, such as mixing the sample with NaCl (in 4 C erythrose) or glycine (in scopine) and then compacting and drying it to create solid rods that would be subsequently ablated by laser radiation, successful. After testing various substances as solidifying agents (i.e., NaCl, glycine, glue (loctite), talcum powder, anhydrous magnesium sulfate, and silica gel), using different proportions (about 25, 50 and 75%) and different drying times, the best results were obtained with a mix of talcum powder and erythrulose in a 50:50 (w/w) ratio with drying times of 2–3 weeks in a vacuum desiccator.…”