Heteronuclear Multiple Quantum Coherence Spectroscopy Research Articles

Synthesis and properties of biobased mono-benzoxazine resins from natural renewable pterostilbene

Two novel fully biobased mono-benzoxazine resins have been designed and synthesized using pterostilbene, furfurylamine/stearylamine and paraformaldehyde via a solventless reaction. The structures of newly obtained mono-benzoxazine monomers have been characterized by nuclear magnetic resonance (NMR) spectroscopy, Fourier transform infrared (FT-IR) spectroscopy and high-resolution mass spectrometry (HR-MS). The detailed assignments for oxazine-ring protons and carbons in each benzoxazine are identified using 1H–13C heteronuclear multiple quantum coherence spectroscopy (HMQC). Besides, the polymerization processes of benzoxazine resins are studied by differential scanning calorimetry (DSC) and in situ FT-IR spectroscopy, and the thermal stability of their corresponding polybenzoxazines are investigated by thermogravimetric analysis (TGA). Moreover, coatings of both polybenzoxazines on glass slides and low-carbon steels have also been prepared to evaluate their anticorrosion performance. The results indicate that both polybenzoxazines possess good thermal stability and can play efficient roles for shielding corrosion as coatings. Therefore, the current study highlights the utility of the natural renewable pterostilbene as a promising candidate to prepare high-performance bio-based polybenzoxazines.

Unique self-catalyzed cationic ring-opening polymerization of a high performance deoxybenzoin-based 1,3-benzoxazine monomer

An asymmetric bis(1,3-benzoxazine) monomer based on deoxybenzoin has been synthesized through Mannich condensation. The chemical structure of this deoxybenzoin-based monomer has been confirmed using 1H NMR, 13C NMR, FT-IR and elemental analysis. The assignments for the oxazine protons and carbon atoms in the asymmetric structure have also been confirmed using two-dimensional (2D) NMR techniques, including 1H-1H nuclear Overhauser effect spectroscopy (NOESY) and 1H-13C heteronuclear multiple quantum coherence spectroscopy (HMQC). In addition, the effect of incorporation of deoxybenzoin on the mode of polymerization of benzoxazine has been investigated using differential scanning calorimetry (DSC), in situ FT-IR and 1H NMR spectroscopy. This deoxybenzoin containing bis(benzoxazine) exhibits a low polymerization temperature resulting from a unique self-catalyzed cationic polymerization mechanism. Furthermore, the thermal stability of the resulting polybenzoxazine has been studied using thermogravimetric analysis (TGA). This deoxybenzoin-based polybenzoxazine exhibits high thermal stability and low flammability, with a Td5 temperature of 403 °C, a high char yield value (68%) and low total heat release (THR of 11.4 kJ/g).

Antiinflammatory and Antioxidant Flavonoids and Phenols from Cardiospermum halicacabum (倒地鈴 Dào Dì Líng)

Seventeen compounds, quercetin-3-O-α-l-rhamnoside (1), kaempferol-3-O-α-l-rhamnoside (2), apigenin-7-O-β-d-glucuronide (3), apigenin 7-O-β-d-glucuronide methyl ester (4), apigenin 7-O-β-d-glucuronide ethyl ester (5), chrysoeriol (6), apigenin (7), kaempferol (8), luteolin (9), quercetin (10), methyl 3,4-dihydroxybenzoate (11), p-coumaric acid (12), 4-hydroxybenzoic acid (13), hydroquinone (14), protocathehuic acid (15), gallic acid (16), and indole-3-carboxylic acid (17), were isolated from the ethanol extract of Taiwanese Cardiospermum halicabum. All chemical structures were determined by physical and extensive spectroscopic analyses such as 1H Nuclear Magnetic Resonance spectroscopy (NMR), 13C NMR, 1H-1H Correlation spectroscopy (1H-1H COSY), Heteronuclear Multiple Quantum Coherence spectroscopy (HMQC), Heteronuclear Multiple-bond Correlation spectroscopy (HMBC), and Nuclear Overhauser Effect spectroscopy (NOESY), as well as comparison with literature values. Furthermore, the High-Performance Liquid Chromatography-Photodiode Array Detector (HPLC-DAD) fingerprint profile was established for the determination of major constituents in the EtOAc extract and retention times of the isolated compounds. All isolated compounds were also evaluated for antiinflammatory and antioxidant activities.

Antiinflammatory and Antioxidant Flavonoids and Phenols from Cardiospermum halicacabum ( Dào Dì Líng).

Seventeen compounds, quercetin-3-O-α-l-rhamnoside (1), kaempferol-3-O-α-L-rhamnoside (2), apigenin-7-O-β-D-glucuronide (3), apigenin 7-O-β-D-glucuronide methyl ester (4), apigenin 7-O-β-D-glucuronide ethyl ester (5), chrysoeriol (6), apigenin (7), kaempferol (8), luteolin (9), quercetin (10), methyl 3,4-dihydroxybenzoate (11), p-coumaric acid (12), 4-hydroxybenzoic acid (13), hydroquinone (14), protocathehuic acid (15), gallic acid (16), and indole-3-carboxylic acid (17), were isolated from the ethanol extract of Taiwanese Cardiospermum halicabum. All chemical structures were determined by physical and extensive spectroscopic analyses such as 1 H Nuclear Magnetic Resonance spectroscopy (NMR), 13C NMR, 1H-1H Correlation spectroscopy (1H-1H COSY), Heteronuclear Multiple Quantum Coherence spectroscopy (HMQC), Heteronuclear Multiple-bond Correlation spectroscopy (HMBC), and Nuclear Overhauser Effect spectroscopy (NOESY), as well as comparison with literature values. Furthermore, the High-Performance Liquid Chromatography- Photodiode Array Detector (HPLC-DAD) fingerprint profile was established for the determination of major constituents in the EtOAc extract and retention times of the isolated compounds. All isolated compounds were also evaluated for antiinflammatory and antioxidant activities.

Structural elucidation and complete assignment of a novel class of sulfonamides: bridgehead tricyclic sultams

AbstractEndocyclic sulfonamide templates bearing both an exocyclic ketone function and an internal olefin underwent reaction with a variety of hydroxylamines to effect an intramolecular nitrone–olefin cycloaddition to afford a new class of compounds suitable for derivatization by high‐throughput medicinal chemistry. Structural elucidation via complete assignment of the 1H and 13C NMR spectra of this new class of compounds was achieved using gradient‐COSY, gradient heteronuclear multiple quantum‐coherence spectroscopy and gradient heteronuclear multiple bond correlation spectroscopy. Additionally, double pulsed field gradient spin echo–nuclear Overhauser effect experiments were carried out in order to study the spatial conformation of this new type of molecule and assess the stereo‐ and regio‐selectivity of the chemical transformation. The unequivocal molecular framework and structural conformation was confirmed by X‐ray diffraction. Copyright © 2002 John Wiley & Sons, Ltd.

New structures of the O-specific polysaccharides of bacteria of the genus Proteus. 1. Phosphate-containing polysaccharides.

The O-specific polysaccharide chains (O-antigens) of the lipopolysaccharides of five Proteus strains, P. vulgaris O17, P. mirabilis O16 and O33, and P. penneri 31and 103, were found to contain phosphate groups that link the non sugar components, e.g., ethanolamine and ribitol. The polysaccharides of P. mirabilis O16 and P. penneri 103 include ribitol phosphate in the main chain and thus resemble ribitol teichoic acids of Gram-positive bacteria. The structures of the polysaccharides were elucidated using NMR spectroscopy, including two-dimensional 1H,1H correlation spectroscopy (COSY and TOCSY), nuclear Overhauser effect spectroscopy (NOESY or ROESY), and H-detected 1H,13C and 1H,31P heteronuclear multiple-quantum coherence spectroscopy (HMQC), along with chemical methods. The structures determined are unique among the bacterial polysaccharides and, together with the data obtained earlier, represent the chemical basic for classification of Proteus strains. Based on structural similarities of the O-specific polysaccharides and serological relationships between the O-antigens, we propose to extend Proteus serogroups O17 and O19 by including P. penneri strains 16 and 31,respectively.

Accumulation of a polyisoprene-linked amino sugar in polymyxin-resistant Salmonella typhimurium and Escherichia coli: structural characterization and transfer to lipid A in the periplasm.

Polymyxin-resistant mutants of Escherichia coli and Salmonella typhimurium accumulate a novel minor lipid that can donate 4-amino-4-deoxy-l-arabinose units (l-Ara4N) to lipid A. We now report the purification of this lipid from a pss(-) pmrA(C) mutant of E. coli and assign its structure as undecaprenyl phosphate-alpha-l-Ara4N. Approximately 0.2 mg of homogeneous material was isolated from an 8-liter culture by solvent extraction, followed by chromatography on DEAE-cellulose, C18 reverse phase resin, and silicic acid. Matrix-assisted laser desorption ionization/time of flight mass spectrometry in the negative mode yielded a single species [M - H](-) at m/z 977.5, consistent with undecaprenyl phosphate-alpha-l-Ara4N (M(r) = 978.41). (31)P NMR spectroscopy showed a single phosphorus atom at -0.44 ppm characteristic of a phosphodiester linkage. Selective inverse decoupling difference spectroscopy demonstrated that the undecaprenyl phosphate group is attached to the anomeric carbon of the l-Ara4N unit. One- and two-dimensional (1)H NMR studies confirmed the presence of a polyisoprene chain and a sugar moiety with chemical shifts and coupling constants expected for an equatorially substituted arabinopyranoside. Heteronuclear multiple-quantum coherence spectroscopy analysis demonstrated that a nitrogen atom is attached to C-4 of the sugar residue. The purified donor supports in vitro conversion of lipid IV(A) to lipid II(A), which is substituted with a single l-Ara4N moiety. The identification of undecaprenyl phosphate-alpha-l-Ara4N implies that l-Ara4N transfer to lipid A occurs in the periplasm of polymyxin-resistant strains, and establishes a new enzymatic pathway by which Gram-negative bacteria acquire antibiotic resistance.

Characterization of N‐acylphosphatidylethanolamine and acylphosphatidylglycerol in oats

Two polar lipid classes, both with three acyl groups, were isolated from an extract of oats and characterized by nuclear magnetic resonance spectroscopy, electrospray mass spectrometry (MS), and electron ionization MS (EIMS). Distortionless enhancement by polarization transfer (DEPT) and the two-dimensional correlation experiments 1H-detected heteronuclear multiple quantum coherence spectroscopy, heteronuclear multiple bond correlation spectroscopy, double quantum filtered correlation spectroscopy, and total correlation spectroscopy provided sufficient information for determination of the structure of the two lipid classes. The polar lipid classes were found to be N-acylphosphatidylethanolamine [1,2-diacyl-sn-glycero-3-phospho-(N-acyl)-1'-ethanolamine; N-acyl-PE] and acylphosphatidylglycerol [1,2-diacyl-sn-glycero-3-phospho-(3'-acyl)-1'-sn-glycerol]. High-performance liquid chromatography with electrospray ionization MS (HPLC-ESMS) and with electrospray ionization tandem MS (HPLC-MS/MS) were utilized for the separation and subsequent determination of molecular species. With HPLC-ESMS, ions of deprotonated molecules were obtained and with HPLC-MS/MS carboxylate ions (representing acyl groups) were obtained as well as other structurally significant ions. Fifty molecular species of N-acylphosphatidylethanolamine and 24 molecular species of acylphosphatidylglycerol were found, with a molecular mass range of 924-1032 Da and 959-1035 Da, respectively. Identification of the fatty acid isomers, as picolinyl ester derivatives, was done with gas chromatography with EIMS. Three isomers of 16:1 fatty acids were found in N-acyl-PE, and their double bond positions were determined to 6, 9, and 11 with a relative abundance of 4:10:1.

Novel Mechanism of Surface Catalysis of Protein Adduct Formation: NMR STUDIES OF THE ACETYLATION OF UBIQUITIN

Reactivity of surface lysyl residues of proteins with a broad range of chemical agents has been proposed to be dependent on the catalytic microenvironment of the residue. We have investigated the acetylation of wild type ubiquitin and of the UbH68N mutant to evaluate the potential contribution of His-68 to the reactivity of Lys-6, which is about 4 A distant. These studies were performed using [1-(13)C]acetyl salicylate or [1,1'-(13)C(2)]acetic anhydride, and the acetylated products were detected by two-dimensional heteronuclear multiple quantum coherence spectroscopy. The results demonstrate that His-68 makes a positive contribution to the rate of acetylation of Lys-6 by labeled aspirin. Additionally, a pair of transient resonances is observed after treatment of wild type ubiquitin with the labeled acetic anhydride but not upon treatment of the H68N mutant. These resonances are assigned to the acetylated His-68 residue. The loss of intensity of the acetylhistidine resonances is accompanied by an increase in intensity of the acetyl-Lys-6 peak, supporting the existence of a transacetylation process between the acetylhistidine 68 and lysine 6 residues located on the protein surface. Hence, this may be the first direct demonstration of a catalytic intermediate forming on the protein surface.

Alkaloid-fullerene systems through photocycloaddition reactions.

The photocycloaddition of tertiary amines to ¿60fullerene (C(60)) is an interesting and useful reaction. We wished to extend the applications of this type of reaction through an investigation of the photoaddition of alkaloids to C(60) for the purpose of synthesizing novel and complex photoadducts that are difficult to obtain by usual methods. Irradiation of tazettine (2) or gramine (3) with C(60) in toluene leads to formation of one monoadduct (6 or 7), whereas scandine (1a) or 10-hydroxyscandine (1b) reacts with C(60) photochemically to give two products, the expected ¿6,6 monoadduct (5a, 5b) and a new type of monoadduct with a bis-¿6, 6 closed structure (4a, 4b). These new structures were characterized by UV-vis, FT-IR, (1)H NMR, (13)C NMR, (1)H-(1)H COSY, ROESY, HMQC (heteronuclear multiple-quantum coherence), and HMBC (heteronuclear multiple-bond connectivity) spectroscopy. The techniques of time-of-flight secondary ion MS (TOF-SIMS) and field desorption MS (FD-MS) were used for the mass determination. (3)He NMR analysis of the product mixture from photoaddition of 1a to C(60) containing a (3)He atom ((3)He@C(60)) led to two peaks at -9.091 and -11.090 ppm relative to gaseous (3)He, consistent with formation of a ¿6, 6-closed monoadduct and a bis-¿6,6 closed adduct. Presumably, the bis-¿6, 6 closed adducts are formed by an intramolecular ¿2 + 2 cycloaddition of the vinyl group to the adjacent 6,6-ring junction of C(60) after the initial photocycloaddition.

High resolution solution structure of the protein part of Cu7 metallothionein.

The three-dimensional solution structure of the protein part of Cu7 metallothionein (Cu7MT) of Saccharomyces cerevisiae has been attempted by 1H two-dimensional NMR spectroscopy at 800 MHz. The protein part constitutes 53 amino acids. A total of 1192 NOEs, of which 1048 are meaningful, were used to determine the solution structure of the first 40 residues, the last 13 residues being disordered. A family of 30 structures was generated. Root-mean-square deviation (rmsd) values from the average structure of 0.32 +/- 0.13 A and 0.61 +/- 0.15 A for backbone and all heavy atoms, respectively, were obtained for the residues 2-40. The ten copper-coordinating cysteine sulfurs and the empty spaces around them are well defined. The structure of the protein part is similar but not identical to the available ones of the same holoprotein and of the Ag7 metallothionein, and is qualitatively superior. If the same metal-sulfur connectivities reported in the literature from 1H-109Ag heteronuclear multiple quantum coherence spectroscopy are assumed to hold for the present copper derivative, a peptide structure is obtained which is again similar, but still not identical, within indetermination, to that available. The structure of the copper polymetallic center may well be different from that proposed for the silver derivative, and indeed a number of different arrangements of the seven copper ions are consistent with the present highly refined structure of the protein part.

Simulation of the off-resonance effect in one-dimensional heteronuclear multiple quantum coherence spectroscopy

When a heteronuclear multiple quantum coherence (HMQC) NMR experiment is performed in one-dimensional mode, due to the wide range in chemical shift of the indirectly detected spin and the limited strength of the radio-frequency field, the off-resonance effect on the intensity of the observed signal can be serious. In this paper, the effect is studied using the spin-density-matrix formalism and simulations of the experimental results are presented. The bilinear rotation-decoupling sequence (BIRD), which is usually used in HMQC experiments, is also discussed. It is shown that the BIRD sequence has a negative effect by virtue of narrowing the excitation band.

750 MHz 1H and 1H-13C NMR spectroscopy of human blood plasma.

High-resolution 750 MHz 1H NMR spectra of control human blood plasma have been measured and assigned by the concerted use of a range of spin-echo, two-dimensional J-resolved, and homonuclear and heteronuclear (1H-13C) correlation methods. The increased spectral dispersion and sensitivity at 750 MHz enable the assignment of numerous 1H and 13C resonances from many molecular species that cannot be detected at lower frequencies. This work presents the most comprehensive assignment of the 1H NMR spectra of blood plasma yet achieved and includes the assignment of signals from 43 low M(r) metabolites, including many with complex or strongly coupled spin systems. New assignments are also provided from the 1H and 13C NMR signals from several important macromolecular species in whole blood plasma, i.e., very-low-density, low-density, and high-density lipoproteins, albumin, and alpha 1-acid glycoprotein. The temperature dependence of the one-dimensional and spin-echo 750 MHz 1H NMR spectra of plasma was investigated over the range 292-310 K. The 1H NMR signals from the fatty acyl side chains of the lipoproteins increased substantially with temperature (hence also molecular mobility), with a disproportionate increase from lipids in low-density lipoprotein. Two-dimensional 1H-13C heteronuclear multiple quantum coherence spectroscopy at 292 and 310 K allowed both the direct detection of cholesterol and choline species bound in high-density lipoprotein and the assignment of their signals and confirmed the assignment of most of the lipoprotein resonances.

Preparation and structural characterization of large heparin-derived oligosaccharides.

Porcine mucosal heparin was partially depolymerized with heparin lyase I and then fractionated into low-molecular-weight (< 5000) and high-molecular-weight (> 5000) oligosaccharides by pressure filtration. The high-molecular-weight oligosaccharide mixture (approximately 50 wt% of the starting heparin) also contained intact heparin. This intact polymer complicates oligosaccharide purification. Thus, the low-molecular-weight fraction was used to prepare homogeneous oligosaccharides for structural characterization. The low-molecular-weight oligosaccharide mixture was first fractionated by low-pressure gel permeation chromatography into size-uniform mixtures of disaccharides, tetrasaccharides, hexasaccharides, octasaccharides, decasaccharides, dodecasaccharides, tetradecasaccharides and higher oligosaccharides. Each size-fractionated mixture was then purified on the basis of charge by repetitive semi-preparative strong-anion-exchange high-performance liquid chromatography. This approach has led to the isolation of 14 homogeneous oligosaccharides from disaccharide to tetradecasaccharide. The purity of these heparin-derived oligosaccharides was determined by gradient polyacrylamide gel electrophoresis, analytical strong-anion-exchange high-performance liquid chromatography, capillary electrophoresis and one-dimensional nuclear resonance spectroscopy. The structure of these oligosaccharides was established using 600 MHz two-dimensional nuclear resonance spectroscopy. The spectral methods used included homonuclear correlation spectroscopy, nuclear Overhauser effect spectroscopy and heteronuclear multiple quantum coherence spectroscopy. The 1H/1H connectivities of the protons of each sugar residue in an oligosaccharide were established by two-dimensional homonuclear correlation spectroscopy, while 1H/13C assignments were made using 1H inverse detection. One- and two-dimensional nuclear resonance spectroscopic analysis of these heparin oligosaccharides showed two closely related groups of heparin-oligosaccharides are afforded by enzymatic depolymerization of heparin. One group is fully sulphated, having the structures delta UAp2S(1[-->4)-alpha-D-GlcNpS6S(1-->4)-alpha-L-IdoAp2S( 1]n-->4)-alpha- D-GlcNpS6S, where delta UAp is 4-deoxy-alpha-L-threo-hex-4-eno-pyranosyluronic acid, GlcNp is 2-deoxy-2-aminoglucopyranose, IdoAp is idopyranosyluronic acid, S is sulphate and n = 0-6. The other group of oligosaccharides differ in that they contain beta-D-glucuronic acid in place of the alpha-L-iduronic acid residue nearest to the reducing end. The present study describes the isolation and structural elucidation of seven new oligosaccharides: an octasaccharide, two decasaccharides, two dodecasaccharides and two tetradecasaccharides. The utility of two-dimensional nuclear resonance spectroscopy to determine the structure of complex heparin oligosaccharides is also illustrated.

NMR study of nitrogen-15-labeled Escherichia coli valine transfer RNA.

1,3-15N-Labeled uracil was synthesized chemically and used to prepare labeled Escherichia coli tRNA(Val) biosynthetically. 500-MHz measurements of 15N and proton chemical shift were obtained, for all uridine and uridine-related bases, by heteronuclear multiple-quantum coherence spectroscopy. All the uracil NH group resonances were assigned and were in agreement with previous proton-only assignments. The temperature dependence of intensities of resonances was used to infer the relative stability of parts of the molecule. The acceptor stem was the least thermally stable structural feature, while the anticodon and T loop were relatively more stable.

Hydrolysis products of cisplatin: pK a determinations via[1H, 15N] NMR spectroscopy

The pKa values of cis-[PtCl(H2O)(NH3)2]+(6.41) and cis-[Pt(H2O)2(NH3)2]2+(5.37 and 7.21) have been determined at 300 K via the use of 15N-edited 1H NMR spectroscopy and [1H, 15N] heteronuclear multiple quantum coherence spectroscopy; this allows rapid measurements at low (millimolar) concentrations, and so avoids some of the problems associated with other methods.

Structure of the De‐O‐acetylated glucuronoxylomannan from Cryptococcus neoformans serotype D, as determined by 2D NMR spectroscopy

AbstractThe primary structure of the de‐O‐acetylated glucuronoxylomannan isolated from Cryptococcus neoformans serotype D was characterized de novo by NMR spectroscopy. Assignment of the 1H and 13C spectra of the polysaccharide involved a combination of 2D NMR experiments including double‐quantum‐filtered {1H,1H} COSY, {1H,1H} TOCSY and 1H‐detected {1H,13C} heteronuclear multiple quantum coherence spectroscopy. The sequence of the glycosyl residues, including the linkage positions, was deduced by {1H,1H} rotating‐frame NOE (ROESY) spectroscopy. The serotype‐D glucuronoxylomannan was found to be a branched polymer with a repeating pentasaccharide unit of the following structure: magnified image.

Solution behavior and complete proton and carbon-13 NMR assignments of the coenzyme B12 derivative (5'-deoxyadenosyl)cobinamide using modern 2D NMR experiments, including 600 MHz proton NMR data

Two-dimensional (2D) NMR methods have been used to assign completely the {sup 1}H and {sup 13}C NMR spectra of the (5{prime}-deoxyadenosyl)cobinamide cation (AdoCbi{sup +}) in D{sub 2}O. Most of the {sup 1}H spectral assignments were made by using 2D homonuclear shift correlation spectroscopy (COSY), homonuclear Hartmann-Hahn spectroscopy (HOHAHA), absorption-mode (phase sensitive) 2D nuclear Overhauser effect (NOE) spectroscopy, and spin-locked NOE spectroscopy (also called ROESY, for rotating-frame Overhauser enhancement spectroscopy). Most of the protonated carbon resonances were assigned by using {sup 1}H-detected heteronuclear multiple-quantum coherence (HMQC) spectroscopy. The nonprotonated carbon resonances, as well as the remaining unassigned {sup 1}H and {sup 13}C NMR signals, were assigned from long-range {sup 1}H-{sup 13}C connectivities determined from {sup 1}H-detected multiple-bond heteronuclear multiple-quantum coherence spectroscopy (HMBC). Comparison of the {sup 13}C chemical shifts and {sup 1}H NOEs of AdoCbi{sup +} with those of coenzyme B{sup 12} ((5{prime}-deoxyadenosyl)cobalamin) and its benzimidazole-protonated, base-off form indicates that the electronic properties and structure of AdoCbi{sup +} are similar to that of coenzyme B{sup 12} in the protonated, base-off form. The {sup 13}C chemical shifts of most of the carbons of AdoCbi{sup +} do not vary significantly from those of base-off, benzimidazole-protonated coenzyme B{sup 12}, indicating that the electronic environmentmore » of the corrin ring is also similar in both compounds. However, significant differences in the chemical shifts of some of the corresponding carbons of the b, d, e, and f corrin side chains in AdoCbi{sup +} and in base-off, benzimidazole-protonated coenzyme B{sub 12} indicate that the positions of these side chains may be different in AdoCbi{sup +} compared to base-off coenzyme B{sup 12}.« less

Biosynthesis of staurosporine, 1. 1H- and 13C-NMR assignments.

Complete and unambiguous assignments of the 1H- and 13C-nmr spectra of the potent antitumor antibiotic staurosporine have been accomplished using a combination of one- and two-dimensional nmr techniques, including one-bond and long-range heteronuclear multiple-quantum coherence spectroscopy (HMQC). Staurosporine was found to be highly cytotoxic in the KB and P-388 assays but was inactive in the microtubulin assembly assay.