Synthesis and isolation of nitro‐bT‐carbolines obtained by nitration of commercial β‐carboline alkaloids

Abstract

Nitration of commercial full aromatic β-carboline alkaloids nor-harmane (1), harmane (2), harmine (3), harmol (4), and the 7-acetylated derivative of harmol (5) is described. Advantages and disadvantages of different nitration reagents which involve acidic conditions (HNO 3 /H + ) and neutral conditions (Cu(NO 3 ) 2 ; ceric ammonium nitrate) are discussed. A complete 1 H and 13 C-nmr characterization including ms and also uv absorption spectra in neutral and acid media is presented. A detailed ei-ms and ld-tof-ms study is enclosed because the nitro-β-carbolines constitute a new family of β-carboline-like chromophores with potential use as matrix in uv-maldi-tof-ms.

Synthesis and isolation of bromo‐β‐carbolines obtained by bromination of β‐carboline alkaloids

“…To begin with, preparation of nitro-β-carbolines [3] and bromo-β-carbolines was selected because, as it is known, for aromatic molecules these groups as substituents induce strong modifications on the acid-base properties in the ground and electronic excited state and on the nature (π,π*; n,π*), multiplicity (singlet, S 1 ; triplet, T 1 ), time of life (τ S1 ; τ T1 ) and efficiency of population (φ) of the electronic excited states [4,5].…”

“…As part of our study of the photochemistry of commercially available azacarbazoles (β-carbolines) [1] and their potential use as matrices (photosensitizers) in matrix assisted ultraviolet laser desorption/ionization time-offlight mass spectrometry (uv-maldi-tof ms) [2], we decided to examine the behavior of substituted β-carbolines. To begin with, preparation of nitro-β-carbolines [3] and bromo-β-carbolines was selected because, as it is known, for aromatic molecules these groups as substituents induce strong modifications on the acid-base properties in the ground and electronic excited state and on the nature (π,π*; n,π*), multiplicity (singlet, S 1 ; triplet, T 1 ), time of life (τ S1 ; τ T1 ) and efficiency of population (φ) of the electronic excited states [4,5].…”

“…The present study reports the preparation of bromo derivatives from β-carbolines (Scheme 1, nor-harmane (1), harmane (2), harmine (3), harmol (4) and 7-acetylharmol (5)) using N-bromosuccinimide as brominating reagent providing for the first time bromo-β-carbolines 3a, 3b, 3c, 3d, 3e, 4a, 4b, 5a, 5b, and 5c. We also describe in detail the use of chromatographic methods (tlc, preparative chromatographic folders and column chromatography) in order to (i) follow the bromination reaction, (ii) determine the yield of the reactions and (iii) isolate for complete characterization (elemental analysis, R f , mp, 1 H-nmr, 13 C-nmr and ms) of the above mentioned bromo-β-carboline derivatives as well as the derivatives 1b, 1c, 1d, 1e, 2a, 2b, 2c, 2d and 2e previously described [6,7].…”

Electronic spectroscopy of the β-carboline derivatives nitronorharmanes, nitroharmanes, nitroharmines and chloroharmines in homogeneous media and in solid matrix

“…The chloro-β-carbolines and the nitro-β-carbolines were synthesized according to the procedures reported elsewhere. 22 Equipment. The absorption measurements were performed with a spectrophotometer Hewlett Packard HP5.…”