Analytical Differentiation of 1‑Alkyl-3-acylindoles and 1‑Acyl-3-alkylindoles: Isomeric Synthetic Cannabinoids

The 1-alkyl-3-acylindoles and the inverse regioisomeric 1-acyl-3-alkylindoles can be prepared directly from a common set of precursor materials and using similar synthetic strategies. The EI mass spectra for these isomers show a number of unique ions which allow for the differentiation of the 1-alkyl-3-acylindole compounds from the inverse regioisomeric 1-acyl-3-alkylindoles. The base peak at <i>m</i>/<i>z</i> 214 in the 1-<i>n</i>-pentyl-3-benzoylindole represents the M-77 cation fragment resulting from the loss of the phenyl group, and this ion is not observed in the inverse isomer. The 1-benzoyl-3-<i>n</i>-pentylindole inverse regioisomer shows a base peak at <i>m</i>/<i>z</i> 105 for the benzoyl cation. Thus, these two base peaks are the result of fragmentation initiated at the carbonyl-oxygen for both isomers. The 1-pentyl-3-benzoylindole is characterized by the strong intensity carbonyl band at 1703 cm^–1, while the amide carbonyl appears as a strong band of equal intensity at 1681 cm^–1 in the 1-benzoyl-3-pentyl regioisomer

Disubstituted piperazine analogues of trifluoromethylphenylpiperazine and methylenedioxybenzylpiperazine: analytical differentiation and serotonin receptor binding studies

<p>A series of N,N-disubstituted piperazines were synthesized containing the structural elements of both methylenedioxybenzylpiperazine (MDBP) and trifluoromethylphenylpiperazine (TFMPP) in a single molecule. These six potential designer drug molecules having a regioisomeric relationship were compared in gas chromatography-mass spectrometry (GC–MS), gas chromatography-infrared spectroscopy and serotonin receptor affinity studies. These compounds were separated by capillary gas chromatography on an Rxi®-17Sil MS stationary phase film and the elution order appears to be determined by the position of aromatic ring substitution.</p> <p>The majority of electron ionization mass spectral fragment ions occur via processes initiated by one of the two nitrogen atoms of the piperazine ring. The major electron ionization mass spectrometry (EI-MS) fragment ions observed in all six of these regioisomeric substances occur at <i>m</i>/<i>z</i> = 364, 229, 163 and 135. The relative intensity of the various fragment ions is also equivalent in each of the six EI-MS spectra. The vapour phase infrared spectra provide a number of absorption bands to differentiate among the six individual compounds on this regioisomeric set. Thus, the mass spectra place these compounds into a single group and the vapour phase infrared spectra differentiate among the six regioisomeric possibilities.</p> <p>All of the TFMPP–MDBP regioisomers displayed significant binding to 5-HT_2B receptors and in contrast to 3-TFMPP, most of these TFMPP–MDBP isomers did not show significant binding at 5-HT₁ receptor subtypes. Only the 3-TFMPP-3,4-MDBP (Compound 5) isomer displayed affinity comparable to 3-TFMPP at 5-HT_1A receptors (<i>K_i</i> = 188 nmol/L).</p

Slow-Binding Inhibition of <i>Mycobacterium tuberculosis</i> Shikimate Kinase by Manzamine Alkaloids

Tuberculosis represents a significant public health crisis. There is an urgent need for novel molecular scaffolds against this pathogen. We screened a small library of marine-derived compounds against shikimate kinase from <i>Mycobacterium tuberculosis</i> (<i>Mt</i>SK), a promising target for antitubercular drug development. Six manzamines previously shown to be active against <i>M. tuberculosis</i> were characterized as <i>Mt</i>SK inhibitors: manzamine A (<b>1</b>), 8-hydroxymanzamine A (<b>2</b>), manzamine E (<b>3</b>), manzamine F (<b>4</b>), 6-deoxymanzamine X (<b>5</b>), and 6-cyclohexamidomanzamine A (<b>6</b>). All six showed mixed noncompetitive inhibition of <i>Mt</i>SK. The lowest <i>K</i>_I values were obtained for <b>6</b> across all <i>Mt</i>SK–substrate complexes. Time-dependent analyses revealed two-step, slow-binding inhibition. The behavior of <b>1</b> was typical; initial formation of an enzyme–inhibitor complex (EI) obeyed an apparent <i>K</i>_I of ∼30 μM with forward (<i>k</i>₅) and reverse (<i>k</i>₆) rate constants for isomerization to an EI* complex of 0.18 and 0.08 min^–1, respectively. In contrast, <b>6</b> showed a lower <i>K</i>_I for the initial encounter complex (∼1.5 μM), substantially faster isomerization to EI* (<i>k</i>₅ = 0.91 min^–1), and slower back conversion of EI* to EI (<i>k</i>₆ = 0.04 min^–1). Thus, the overall inhibition constants, <i>K</i>_I*, for <b>1</b> and <b>6</b> were 10 and 0.06 μM, respectively. These findings were consistent with docking predictions of a favorable binding mode and a second, less tightly bound pose for <b>6</b> at <i>Mt</i>SK. Our results suggest that manzamines, in particular <b>6</b>, constitute a new scaffold from which drug candidates with novel mechanisms of action could be designed for the treatment of tuberculosis by targeting <i>Mt</i>SK