13C NMR Signals Research Articles

Synthesis, 13C NMR, and UV spectroscopic study of 13C-labeled nitrile N-oxide

13C-labeled nitrile N-oxides (13CNOs) were prepared to investigate the structural characteristics of nitrile N-oxide in solution. In the 13C NMR spectra at room temperature, 13C signals of 13CNOs appeared at 35–38ppm. The chemical shift of adjacent aromatic carbon Ca to 13CNO was remarkably upfield-shifted to indicate a positive mesomery effect of CNO. The 13C NMR signal appeared as a triplet that originated from the scalar coupling of the adjacent 14N nucleus, while it fused into a singlet as the temperature decreased. The UV spectra of 13CNOs also indicated the temperature-dependent dynamic character of CNO.

English

A small library of benzimidazoles with a range of side-chain substituents have been synthesized through the condensation reaction of o-phenylenediamine derivatives and several other commercially available materials. The reactions were catalyzed by either 4M HCl or 1,3-dibromo-5,5-dimethylhydantoin (DBDMH). The compounds synthesized using DBDMH as the catalyst required a shorter reaction time, the yield was higher and the workup procedure was not as tedious as those produced using 4M HCl as the catalyst. The structural elucidations of synthesized compounds have been confirmed through spectroscopic analysis. 13C NMR analysis of some of the synthesized compounds showed that the appearance of carbon signals in the NMR spectrum is affected by the nature of the NMR solvent and temperature.The exchange-induced broadening of the 13C NMR signal was probably facilitated by the intermolecular proton exchange between the NH of the benzimidazole and the H2O present in the DMSO-d6 solvent. Key words: 1,3-dibromo-5,5-dimethylhydantoin, benzimidazole, solvent-effect, structure elucidation, synthetic method.

Sandwich-type lanthanide(III) complexes of a tetraiminodiphenol macrocyclic ligand derived from 4-methyl-2,6-diformylphenol and 1,3-diaminopropane: structure, NMR and luminescence

The macrocyclic ligand salt [H2LH2](ClO4)2, derived from the [2+2] condensation process involving 4-methyl-2,6-diformylphenol and 1,3-diaminopropane, has been used to synthesize the sandwich-type lanthanide(III) complexes [Ln(LH2)2](ClO4)3·2H2O (1–6, Ln=La–Eu, except Pm), [Ln(LH2)2](ClO4)3·CH3CN (7–13, Ln=Gd–Lu, except Er) and [Ln(LH2)(LH)](BPh4)2 (14–16, Ln=La, Nd and Sm). The X-ray crystal structures of the compounds 1, 7, 12, 13, 14 and 15 have been determined. In the isostructural [Ln(LH2)2](ClO4)3·CH3CN complexes of Gd (7), Yb (12) and Lu (13), the two macrocyclic ligands are considerably folded, albeit to different extents, and not symmetrically bound to the metal center. In these compounds, the metal center is coordinated with two imine nitrogen atoms and two phenolate oxygen atoms of each of the ligands (LH2), whose two other uncoordinated imine nitrogens are protonated and intramolecularly hydrogen-bonded with the phenolate oxygens. The structures determined for the La (14) and Nd (15) complexes of [Ln(LH2)(LH)](BPh4)2 are found to be identical. In these complexes, the ligand LH contains one N–H⋯O hydrogen-bonded unit, as against two in the ligand LH2. The [Ln(N2O2)2] coordination polyhedron in all the cases is a distorted square antiprism, although the extent of distortion in 7, 12 and 13 is less compared to that in 14 and 15. 1H NMR spectra of the [Ln(LH2)2]3+complexes in solution indicate a C2 symmetry. The 1H and 13C NMR signals of the EuIII complex 6 have been assigned on the basis of COSY, DEPT, HMQC and NOESY spectra. The photoluminescence spectra of the Sm(III) (5) and Eu(III) (6) complexes have been studied in a methanol–ethanol (1:4) glassy matrix at 77K. The luminescence intensity of the hypersensitive 5D0→7F2 transition in 6 increases with the addition of triethylamine due to the formation of [Eu(LH2)(LH)]2+ and [Eu(LH)2]+ species, which in turn partially attenuate the quenching effect of the N–H⋯O oscillators on the emitting states of the metal ion.

Synthesis and Spectroscopic Properties of 2,3-Diphenyl-1,3-thiaza-4-one Heterocycles

Synthetic and spectroscopic data (1H NMR, 13C NMR, IR, UV/Vis) for a series of six 2,3-diphenyl-1,3-thiaza-4-one heterocycles which differ in ring size and substitution is reported. The results show that there are significant differences in spectroscopic signals common to all six compounds. Distinctions can be made among the compounds using the IR absorbance of the C4 carbonyl and the 1H NMR signal at C2, and to a lesser extent the 13C NMR signal at C4 and the UV/Vis spectrum.{The equation can be found in the PDF file}.

Crystallographic and spectroscopic study on a known orally active progestin

6,17α-Dimethyl-4,6-pregnadiene-3,20-dione (medrogestone, 2) is for a long time known steroid endowed with progestational activity. In order to study its crystallographic and NMR spectroscopic properties with the aim to fill the literature gap, we prepared medrogestone following a traditional procedure. A careful NMR study allowed the complete assignment of the 1H and 13C NMR signals not only of medrogestone but also of its synthetic intermediates. The structural and stereochemical characterizations of medrogestone together with its precursor 17α-methyl-3-ethoxy-pregna-3,5-dien-20-one were described by means of X-ray analysis, allowing a deepened conformational investigation.

Characterization of Kerogen and Source Rock Maturation Using Solid-State NMR Spectroscopy

Solid-state NMR methods common to the analysis of polymers and other rigid solids are utilized for the study of kerogen, bitumen, and the organic content in source rocks. The use of straightforward nondestructive techniques, primarily employing solid-state NMR, is shown to provide useful information about both individual samples and changes between samples that cover a range of thermal maturities of type II kerogen. In addition to aromatic fraction and chemical structure, one of the most striking changes to isolated kerogen with maturity is the distribution of pore sizes, studied with both 129Xe NMR and complementary nitrogen physisorption, that may help to understand the process of bitumen generation. Ultimately, direct in situ analysis of source rock samples that allow kerogen and bitumen to be distinguished is desirable, as it would eliminate the time and effort to isolate and prepare kerogen samples. By proper consideration and removal of the background, we find that a clear 13C NMR signal can be obta...

A Novel Synthesis of 2,3‐Dihydro‐1,3‐­methano‐1H‐indene {(Bicyclo[2.1.1]hexeno)benzene} and Analysis of Its NMR Spectra

AbstractA new synthesis of 2,3‐dihydro‐1,3‐methano‐1H‐indene (3) has been designed with bicyclo[2.1.1]hex‐2‐ene serving as starting material, which was added onto chloro‐substituted α‐pyrones. The title hydrocarbon 3 was then obtained in two subsequent steps. The AA′MM′ 1H NMR spectrum of 3 was analyzed and simulated, leading to corrections of previously published coupling constants. The 13C NMR signal of the methylene carbon atoms appears at particularly low field (δ = 63.3 ppm). This finding is discussed together with anomalous low‐ and high‐field absorptions of methylene carbon atoms of cyclobutanes and bridgehead carbon atoms of bicyclo[1.1.0]butanes, the 1,3‐ and 2,4‐positions of which, respectively, are bridged by π electron systems. As a result, moieties with (4n + 2) π electrons cause deshieldings, whereas those having 4n π electrons evoke shieldings.

Maintenance-Free Cellulose Solvents Based on Onium Hydroxides

Here, we report maintenance-free cellulose solvents that dissolve much cellulose within a few minutes under mild conditions even in the presence of water. We have examined a series of aqueous solutions of tetraalky-phosphonium and tetraalkyl-ammonium hydroxides to clarify the effect of cation species on cellulose dissolving. Aqueous solutions of the many hydroxides examined here were found to dissolve cellulose at room temperature, and electrostatic interaction and/or steric hindrance of component ions are suggested to affect the cellulose-dissolving ability. In spite of increasing water content after dissolution of wet cellulose, the water content automatically reduced to less than 60% just by keeping the filtrated solution in the air. The solvation state of cellulose in aqueous onium hydroxide solutions is discussed with 13C NMR chemical shift of cellobiose signals in these solutions. They dissolve cellulose only when the 13C NMR signal of the carbon atom at the 12 position of cellobiose is 64.8 ppm or ...

Organoboranes and tetraorganoborates studied by 11B and 13C NMR spectroscopy and DFT calculations

Abstract Care should be taken on recording the sometimes elusive 13C NMR signals for boron-bonded carbon atoms, since it is easy to extract information about coupling constants 1 J(13C,11B) by measuring the respective line widths of 13C(B-C) and 11B NMR signals. This information can be confirmed by quantum-chemical calculations [B3LYP (6-311+G(d,p) level of theory] of n J(13C,11B) in organoboranes and tetraorganoborates. For the latter, the signs for n = 2, 3, 4 were experimentally determined.

A New N-Acyl Taurine from the South China Sea Marine Sponge Callyspongia sp.

The genus Callyspongia (order Haplosclerida, family Callyspongiidae) is widely distributed and contains various bioactive constituents [1]. In the course of our investigation on the marine sponge Callyspongia species, we have reported some metabolites [2, 3]. Further investigation on the marine sponge Callyspongia species has led to the isolation and characterization of a new N-acyl taurine (1). The sponge Callyspongia sp. was collected off the coast of Hainan Island, South China Sea, in January, 2007. The specimen was identified by Dr. Kyung Jin Lee. A voucher specimen (No. 20070101) was deposited in Natural History Museum, Hannam University, Daejon, Korea and Guangdong Key Laboratory of Marine Materia Medica, South China Sea Institute of Oceanology, Chinese Academy of Sciences, China. The wet marine sponge Callyspongia sp. (10 kg) was extracted with ethanol (90%). The ethanol was evaporated in vacuo to afford a syrupy residue that was suspended in distilled water and fractionated successively with petroleum ether, ethyl acetate, and n-butanol. The n-butanol soluble portion (80.1 g) was subjected to RP chromatography eluted with H2O–MeOH (9:1, fr. A), H2O–MeOH (8:2, fr. B), H2O–MeOH (7:3, fr. C), H2O–MeOH (6:4, fr. D), H2O–MeOH (4:6, fr. E), and H2O–MeOH (0:10, fr. F), to give six fractions. Fraction C (4.12 g) was subjected to silica gel chromatography with CHCl3–MeOH (8:2 to 6:4, gradient) to give three fractions (C1–C3). Fraction C2 (435 mg) was subjected to silica gel chromatography with CHCl3–MeOH (8:2), then purified by Sephadex LH-20 (CHCl3–MeOH, 1:1) to afford 1 (5.0 mg). Compound 1 was obtained as a yellow oil, and its molecular formula was deduced to be C13H25NO4S on the basis of the HR-ESI-MS spectrum at m/z 290.1422 [M – H]– (calcd 290.1426 for C13H24NO4S) and NMR data. The gross structure was determined by the aid of COSY, HMQC, and HMBC experiments. The 1H NMR, 13C NMR, and DEPT data for 1 indicated the presence of two methyls, eight sp3 methylenes, one sp2 methine, and two sp2 quaternary carbons. The sulfur and remaining three oxygens in the molecular formula suggested a sulfonic acid group (SO3H). The 1H NMR signals at 3.63 (2H, t, J = 7.0 Hz, H-1 ) and 3.00 (2H, t, J = 7.0 Hz, H-2 ), and 13C NMR signals at C 174.6 (C-1), 36.6 (C-1 ) and 51.5 (C-2 ), together with the HMBC correlations (Fig. 1) of H-2 with C-1 and H-2 with C-1 and C-1 , indicated the two methylenes C-1 and C-2 to be located between the amide and the sulfonic acid, which revealed a taurine moiety in the structure of 1 [4, 5]. The position of the double bond was ascertained at C-3 and C-4 on the basis of the HMBC correlations of H-4 with C-2 and H-5 with C-3. The methyl group (C-11) was determined to be located at C-3 by the HMBC correlations of H-11 with C-2 and C-4. The geometry of the double bond was deduced to be cis based on the chemical shifts of the allylic carbon C-5 at 29.2, which agreed well with the chemical shift for the allylic carbons of cis-olefins (approximately 29) [6]. Thus, the structure of compound 1 was elucidated as 2-(3-methyl-dec-3-enamido)ethanesulfonic acid. 2-(3-Methyl-dec-3-enamido)ethanesulfonic Acid (1). Yellow oil. 1H NMR (500 MHz, CDCl3, , ppm, J/Hz): 5.36 (1H, t, J = 6.5, H-4), 3.63 (2H, t, J = 7.0, H-1 ), 3.00 (2H, t, J = 7.0, H-2 ), 2.91 (2H, s, H-2), 2.07 (2H, m, H-5), 1.77 (3H, s, H-11), 1.18–1.27 (8H, overlap, H-6–9), 0.93 (3H, t, J = 6.5, H-10). 13C NMR (125 MHz, CDCl3, , ppm): 174.6 (C-1), 131.2 (C-4), 130.2 (C-3), 51.5 (C-2 ), 48.8 (C-2), 36.6 (C-1 ), 29.2 (C-5), 23.7–30.8 (C-6–9), 16.3 (C-11), 14.6 (C-10). HR-ESI-MS m/z 290.1422 [M – H]– (calcd 290.1426 for C13H24NO4S).

Conformational state of β-hydroxynaphthylamides: Barriers for the rotation of the amide group around CN bond and dynamics of the morpholine ring

Three β-hydroxynaphthylamides (morpholine, pyrrolidine and dimethylamine derivatives) have been synthesized and their conformational state was analyzed by NMR, X-ray and DFT calculations. In aprotic solution the molecules contain intramolecular OHO hydrogen bonds, which change into intermolecular ones in solid state. The energy barriers for the amide group rotation around the CN bond were estimated from the line shape analysis of 1H and 13C NMR signals. A tentative correlation between the barrier height and the strength of OHO bond was proposed. Calculations of the potential energy profiles for the rotations around CC and CN bonds were done. In case of morpholine derivative experimental indications of additional dynamics: chair–chair ‘ring flip’ in combination with the twisting around CC bond were obtained and confirmed by quantum chemistry calculations.

Near-silence of isothiocyanate carbon in (13)C NMR spectra: a case study of allyl isothiocyanate.

(1)H and (13)C NMR spectra of allyl isothiocyanate (AITC) were measured, and the exchange dynamics were studied to explain the near-silence of the ITC carbon in (13)C NMR spectra. The dihedral angles α = ∠(C1-C2-C3-N4) and β = ∠(C2-C3-N4-C5) describe the conformational dynamics (conformation change), and the bond angles γ = ∠(C3-N4-C5) and ε = ∠(N4-C5-S6) dominate the molecular dynamics (conformer flexibility). The conformation space of AITC contains three minima, Cs-M1 and enantiomers M2 and M2'; the exchange between conformers is very fast, and conformational effects on (13)C chemical shifts are small (νM1 - νM2 < 3 ppm). Isotropic chemical shifts, ICS(γ), were determined for sp, sp(x), and sp(2) N-hybridization, and the γ dependencies of δ(N4) and δ(C5) are very large (10-33 ppm). Atom-centered density matrix propagation trajectories show that every conformer can access a large region of the potential energy surface AITC(γ,ε,...) with 120° < γ < 180° and 155° < ε < 180°. Because the extreme broadening of the (13)C NMR signal of the ITC carbon is caused by the structural flexibility of every conformer of AITC, the analysis provides a general explanation for the near-silence of the ITC carbon in (13)C NMR spectra of organic isothiocyanates.

Structural features of lignohumic acids

The composition and structure of humic acids isolated from lignohumate, which is produced by hydrolytic–oxidative conversion of technical lignosulfonates, were characterized by chemical and spectral methods (UV/VIS, FTIR, and 13C NMR spectroscopy). As comparative samples, humic acids (HA) were isolated also from lignite and organic horizon of mountain spruce forest soil. When compared with other HA studied, the lignohumate humic acids (LHHA) contained relatively few carboxyl groups, whose role is partly fulfilled by sulfonic acid groups. Distinctive 13C NMR signal of methoxyl group carbons, typical for lignin and related humic substances, was found at the shift of 55.9ppm. Other alkoxy carbons were present in limited quantity, like the aliphatic carbons. Due to the low content of these carbon types, the LHHA has high aromaticity of 60.6%.Comparison with the natural HA has shown that lignohumate obtained by thermal processing of technical lignosulfonate can be regarded as an industrially produced analog of natural humic substances. Based on the chemical and spectral data evaluation, structural features of lignohumate humic acids were clarified and their hypothetical chemical structure proposed, which described typical “average” properties of the isolated fraction.

Chemical differences of aquatic humic substances extracted by XAD-8 and DEAE-cellulose

Chemical characteristics of dissolved organic matter (DOM) extracted from an ombrotrophic bog in northern Minnesota by two methods – XAD-8 and DEAE-cellulose – were compared using 13C NMR spectroscopy, excitation–emission matrix fluorescence spectroscopy (EEMS), and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). DOM extracted with XAD-8, a relatively hydrophobic sorbent, had a larger 13C NMR signal in the aromatic carbon region, but DOM extracted by DEAE-cellulose, a weak anion exchanger, had a larger signal in the carboxylic carbon region. DOM extracts prepared by the two methods were similar in their overall chemical characteristics that serve as proxies for organic matter sources. For example, only small differences were observed in the fluorescence index (FI) values of the extracts, and all values were within the range expected for terrestrially-derived DOM. EEMS spectra of both extracts had “humic-like” peak A areas smaller than that of standard reference Suwannee River fulvic acid. Of 2801 distinct chemical formulas assigned during FT-ICR MS analysis of the two extracts, 66% were present in both; 15% were unique to the XAD-8 extract, and 19% were unique to the DEAE-cellulose extract. Van Krevelen plots showed that the DEAE-cellulose extract had more tannin-like and condensed aromatic entities and formulas with higher O/C ratios, whereas the XAD-8 extract had more lignin-like material and formulas with higher H/C ratios. Overall, differences in chemical characteristics of the extracts reflect the mechanisms by which the extractants operate.

Characterization of Tenofovir Disoproxil Fumarate and Its Behavior under Heating

Tenofovir disoproxil fumarate (TDF) is a nucleotide reverse transcriptase inhibitor used worldwide to treat AIDS. The aim of this study was to investigate the structural and dynamic properties of the polymorphic form I of the drug by thermal analysis, Fourier transform infrared spectroscopy, solid-state NMR, and powder X-ray diffraction. A full assignment of 13C NMR resonances was achieved for the first time. Variable-temperature studies were conducted, and the results were related to changes in the TDF structure and dynamics of specific molecular fragments, especially of the fumarate portion of the molecule. It was found that, under heating, the 13C NMR signals related to the carbon atoms of the disoproxil fumarate moiety split into two resonances. The region of the phosphonate vicinity also changes. This can reflect the lack of symmetry of the two molecules in the asymmetric unit after heating. This solid–solid transformation was related to DSC and XRD observations.

EurJOC Has Come a Long Way

EurJOC Has Come a Long Way

Enhancement of quantum rotor NMR signals by frequency-selective pulses

Quantum-rotor-induced polarisation (QRIP) enhancement is exhibited by substances which contain freely rotating methyl groups in the solid state, provided that the methyl groups contain a 13C nucleus. Strong signal enhancements are observed in solution NMR when the material is first equilibrated at cryogenic temperatures, then rapidly dissolved with a warm solvent and transferred into an NMR magnet. QRIP leads to strongly-enhanced 13C NMR signals, but relatively weak enhancements of the 1H signals. We show that the 1H signals suffer from a partial cancellation of degenerate contributions, which may be corrected by applying a frequency-selective π pulse to the inner peaks of the 13C multiplet prior to 1H observation.

Hydrophobization of Silica Aerogels: Insights from Quantitative Solid-State NMR Spectroscopy

Silica aerogels have exceptional physical and chemical properties related to their nanoporous structure and high specific surface area. The hydrophobization of the silica surfaces, for example by modification with trimethylsilyl groups (TMS), is of central importance for silica aerogel production by ambient drying methods, particularly on an industrial scale. This study monitored the chemical modification of silica aerogels by quantitative and two-dimensional solid-state NMR spectroscopy. A series of two-step, acid/base-catalyzed silica alcogels were hydrophobized for different times in hexamethyldisiloxane (HMDSO) and subsequently dried at ambient pressure. Two-dimensional 1H–29Si heteronuclear correlation NMR spectroscopy confirms that both ethoxy and TMS groups are chemically bonded to the silica surfaces. For the single-pulse spectra, a procedure to calibrate the absolute 1H, 13C, and 29Si NMR signal intensities with external references was developed. The quantification procedure is validated by the internal consistency between the 1H, 13C, and 29Si results and the agreement between the measured sample mass and that predicted from the NMR data. The quantitative speciation data on the aerogel samples show that the silica surface is covered by a monolayer of ethoxy, TMS, and silanol groups. Silanol groups are progressively replaced by TMS groups with increasing modification time, and the TMS content has a strong effect on the density of the final aerogel.

Synthesis of an Advanced Model of Zetekitoxin AB Focusing on the N‐Acylisoxazolidine Amide Structure Corresponding to C13–C17

AbstractZetekitoxin AB (ZTX) is a neurotoxin bearing a saxitoxin core structure together with a characteristic nine‐membered macrocyclic lactam involving a N‐acylisoxazolidine moiety and a N‐hydroxylcarbonylmethyl group. We describe a synthesis of an advanced model for ZTX bearing saxitoxin core structure with N‐acylisoxazolidine moiety, i.e., C13–C17. In this synthesis, the isoxazolidine amide moiety of a ZTX analogue was constructed by reaction of an isoxazolidine with the carboxylic acid at C13 of STX, which was obtained by oxidation of the axially oriented alcohol at C13 2‐azaadamantane N‐oxyl (AZADO) in the presence of NaClO and NaClO2. The 13C NMR signal of C13 in the resulting ZTX analogue was discussed by comparison with the reported spectral data for natural product of ZTX.

Chemical Constituents of Arabidopsis thaliana

Arabidopsis thaliana (L.) Heynh. has become a model system for studying many aspects of plant biology and biochemistry. Studies on the chemical constituents have previously led to the isolation of flavonoids [1, 5], oxylipins [2–5], and alkaloids [5] from A. thaliana. The wild herbs of Arabidopsis thaliana were collected from Jiande, Zhejiang, P. R. China, in 2009. A voucher specimen was deposited in the Herbarium of Materia Medica, School of Pharmacy, Second Military Medical University, Shanghai, P. R. China. The dried and powdered material (5 kg) was extracted with 95% EtOH at room temperature. The combined extract was then suspended with water and extracted three times with ethyl acetate, then purified by column chromatography with silica gel to yield compounds 1–7. The compounds were identified using UV, IR, and NMR spectral data and determined as camalexin (1) [6], methyl 1-methyl-1H-indole-3-carboxylate (2) [7, 8], methyl 1H-indole-3-carboxylate (3) [9, 10], 1-methoxy-3-indolecarbaldehyde (4) [11, 12], 4-hydroxy-3-methoxybenzaldehyde (5) [13, 14], phthalic acid isodibutyl ester (6) [15, 16], and -tocopherol (7) [17]. Compounds 1–3 and 5–7 were isolated from A. thaliana for the first time. The 13C NMR signals of compounds 2 were assigned by 1D and 2D NMR for the first time. Camalexin (1). Colorless needles, mp 135–139 C. 1H NMR (400 MHz, CDCl3, , ppm, J/Hz): 9.40 (br.s, N-H), 8.27 (d, J = 7.84, H-4), 7.88 (d, J = 3, H-4 ), 7.84 (d, J = 2.5, H-2), 7.44 (m, H-7), 7.35 (m, H-6), 7.34 (m, H-5), 7.29 (d, J = 3, H-5). 13C NMR (100 MHz, CDCl3, , ppm): 163.6 (s, C-2 ), 142.2 (d, C-2), 136.5 (s, C-7a), 124.9 (s, C-3a), 124.6 (d, C-4 ), 123.1 (d, C-5), 121.4 (d, C-6), 120.4 (d, C-4), 116.1 (d, C-5 ), 112.0 (s, C-3), 111.8 (d, C-7). Methyl 1-Methyl-1H-indole-3-carboxylate (2). White powder. 1H NMR (400 MHz, CDCl3, , ppm): 8.20 (m, H-4), 7.80 (s, H-2), 7.38 (m, H-7), 7.34 (m, H-5), 7.31 (m, H-6), 3.93 (s, OCH3), 3.85 (s, NCH3). 13C NMR (100 MHz, CDCl3, , ppm): 165.5 (COOCH3), 137.2 (s, C-7a), 135.2 (d, C-2), 126.6 (s, C-3a), 122.8 (d, C-5), 121.9 (d, C-6), 121.7 (d, C-4), 109.8 (d, C-7), 106.9 (s, C-3), 51.0 (q, OCH3), 33.5 (NCH3). Methyl Indole-3-carboxylate (3). White powder. 1H NMR (400 MHz, CDCl3, , ppm, J/Hz): 8.65 (br.s, N-H), 8.21 (m, H-4), 7.96 (d, J = 1.12, H-2), 7.45 (m, H-7), 7.32 (m, H-5), 7.30 (m, H-6), 3.95 (s, OCH3). 13C NMR (100 MHz, CDCl3, , ppm): 165.6 (s, COOCH3), 135.9 (s, C-7a), 130.9 (d, C-2), 125.8 (s, C-3a), 123.3 (d, C-5), 122.1 (d, C-6), 121.6 (d, C-4), 111.5 (d, C-7), 108.9 (s, C-3), 51.1 (q, OCH3). Compound 3 displayed significant growth inhibition against K562 human chronic leukemia [18]. 1-Methoxy-3-indolecarbaldehyde (4). Yellow oil. 1H NMR (400 MHz, CDCl3, , ppm): 9.99 (CHO), 8.34 (m, H-7), 7.92 (s, H-2), 7.51 (m, H-4), 7.41 (m, H-6), 7.36 (m, H-5), 4.20 (s, OCH3). 13C NMR (100 MHz, CDCl3, , ppm): 184.2 (s, CHO), 132.6 (d, C-7), 131.7 (d, C-2), 124.6 (d, C-5), 123.5 (d, C-4), 122.2 (s, C-3a), 121.6 (s, C-7a), 114.1 (s, C-3), 108.7 (d, C-6), 66.9 (q, OCH3). 4-Hydroxy-3-methoxybenzaldehyde (5). White powder. 1H NMR (400 MHz, CDCl3, , ppm, J/Hz): 9.85 (CHO), 7.44 (1H, d, J = 1.6, H-2), 7.07 (1H, d, J = 8.5, H-5), 7.46 (1H, dd, J = 8.5, 1.6, H-6), 6.20 (br.s, 4-OH), 3.99 (s, OCH3). 13C NMR (100 MHz, CDCl3, , ppm): 190.6 (s, CHO), 151.6 (s, C-4), 147.1 (s, C-3), 129.9 (s, C-1), 127.5 (d, C-6), 114.4 (d, C-2), 108.7 (d, C-5), 56.1 (q, OCH3).