The crystal and molecular structure of isoalfileramine dihydrobromide

The crystal and molecular structure of isoalfileramine dihydrobromide has been determined from 3-dimensional single crystal X-ray diffraction data collected by counter techniques. Isoalfileramine is a cyclized derivative of the novel alkaloid, alfileramine, which has been isolated from leaves of Zanthoxylum punctatum Vahl. The crystals of isoalfileramine dihydrobromide were triclinic, space group P1? (No. 2), with two formula units in a unit cell of dimensions a = 16.380(12) Å, b = 9.917(7) A, c = 10.648(7) A, α = 116.39(2)°, β = 91.10(2)° and γ = 101.40(2)°. The structural model, which employed anisotropic thermal parameters only for the bromide ions, was refined using full matrix least squares methods to an R value of 0.089 (R_w = 0.090) for 1053 independent reflections with F² > 3σ(F²). Isoalfileramine dihydrobromide is shown to be a unique pentacycle exhibiting a strained pyran ring. This work was critical in establishing structure for the parent alkaloid, alfileramine, and pointed out the clear structural relationship of alfileramine to tetrahydrocannabinols.     

Bishordeninyl Terpene Alkaloids from Zanthoxylum Integrifoliolum

Examination of the leaves of Zanthoxylum integrifoliolum led to the isolation of a new bishordeninyl alkaloid, integramine, along with alfileramine, α‐allocryptopine, pseudoprotopine and (+)‐sesamin from the tertiary non‐phenolic base fraction. The structures of these compounds were elucidated by spectral evidence.     

La méthoxy-12Δ14-vincamine,nouvel alcaloïde isole du Crioceras dipladeniiflorus (Staff) K. Schumann (Apocynacées)

A new indol alkaloid has been isolated from the root barks of Crioceras dipladeniiflorus, whose structure, methoxy-12 Δ¹⁴ vincamine, has been determined by physical methods (NMR spectra and paramagnetic shifts induced by Europium salts).     

Alkaloids of the flora of Mongolia V. Turpelline — A new alkaloid fromAconitum turczaninowii

In the course of a further study of the alkaloids of the epigeal part of Aconitum turczaninowiia new alkaloid has been isolated, which has been named turpelline. A structure for turpelline has been proposed on the basis of a study of its IR, mass, PMR, ¹³ C NMR, and 2D COSY spectra.     

Ishigadine A,a new canthin-6-one alkaloid from an Okinawan marine sponge Hyrtios sp.

A new indole alkaloid with the canthin-6-one skeleton, ishigadine A, has been isolated from an Okinawan marine sponge Hyrtios sp. The structure of ishigadine A was elucidated on the basis of spectroscopic analyses. Ishigadine A is a new canthin-6-one alkaloid possessing a hydroxy group, a 1,3-dimethyl-4-methylthioimidazolium, and a 1-propylguanidine. Ishigadine A is the third canthin-6-one alkaloid from sponges. Ishigadine A might be generated from l-arginine, l-histidine, and l-tryptophan. Ishigadine A exhibited moderate cytotoxicity against L1210 murine leukemia cells.     

Geissospermiculatine,a New Alkaloid from Geissospermum reticulatum Bark

A new alkaloid, geissospermiculatine was characterized in Geissospermum reticulatum A. H. Gentry bark (Apocynaceae). Here, following a simplified isolation protocol, the structure of the alkaloid was elucidated through GC-MS, LC-MS/MS, 1D, and 2D NMR (COSY, ROESY, HSQC, HMBC, ¹H-¹⁵N HMBC). Cytotoxic properties were evaluated in vitro on malignant THP-1 cells, and the results demonstrated that the cytotoxicity of the alkaloid (30  μg/mL) was comparable with staurosporine (10  μM). Additionally, the toxicity was tested on zebrafish (Danio rerio) embryos in vivo by monitoring their development (0–72 h); toxicity was not evident at 30  μg/mL.     

On the alkaloids of strychnos—XXXI: 15-hydroxystrychnine,a new alkaloid from strychnos nux vomica l

The structure of a new alkaloid, the 15-hydroxystrychnine 12, isolated from seeds of Strychnos nux vomica L., has been established by analysis of spectroscopic data of 12 and of its O-acetyl derivative 13. The ¹³C NMR spectrum of the O-acetyl derivative is in agreement with the proposed structure.     

Calyciphylline G, a novel alkaloid with an unprecedented fused-hexacyclic skeleton from Daphniphyllum calycinum

Calyciphylline G (1), a novel Daphniphyllum alkaloid with an unprecedented fused-hexacyclic skeleton containing a 5-azatricyclo[6.2.1.0^1,5]undecane ring, has been isolated from the stem of Daphniphyllum calycinum (Daphniphyllaceae), and the structure and relative stereochemistry were elucidated on the basis of spectroscopic data.     

Plakoridine C, a novel piperidine alkaloid from an Okinawan marine sponge Plakortis sp.

A new piperidine alkaloid plakoridine C (1) has been isolated from an Okinawan marine sponge Plakortis species, and the structure was elucidated from spectroscopic data. Plakoridine C (1) is a new alkaloid possessing a piperidine ring connected to a β-keto-γ-lactone through a double bond.     

Two new tryptamine-derived alkaloids from Chimonanthus praecox f. concolor

A new pyrrolidinoindoline-type alkaloid, CPC-1, and a new tryptamine-derived dimeric alkaloid, CPC-2, were isolated from the seeds and rinds of Chimonanthus praecox f. concolor. The structure including the absolute configuration of CPC-1 was determined by chiral total synthesis. CPC-2 has a unique hexahydropyrroloquinoline skeleton.     

First enantioselective synthesis of the antitumour alkaloid (+)-crispine A and determination of its enantiomeric purity by 1H NMR

A simple enantioselective synthesis of the pyrrolo[2,1-a]isoquinoline alkaloid (+)-crispine A, based on the use of an asymmetric transfer hydrogenation as the key step, is described. The enantiomeric excesses of the obtained alkaloid samples were determined from ¹H NMR spectra recorded in the presence of (+)-(R)-t-butylphenylphosphinothioic acid as a chiral solvating agent.     

Leucolusine, a tetracyclic alkaloid with a novel ring system incorporating an oxindole moiety and fused piperidine-tetrahydrofuran rings

A tetracyclic ring-opened oxindole alkaloid, possessing an unprecedented ring system incorporating fused piperidine-tetrahydrofuran rings, has been isolated from the Malayan species, Leuconotis griffithii. The structure was established by analysis of the spectroscopic data and a possible biogenetic pathway from an Aspidosperma precursor is presented.     

Structure of lilidine

The new alkaloid lilidine, isolated for the first time from the epigeal part ofLilium martagon has been studied by special methods. It has the composition B₅H₆NO₂, mp 118–110°C, [α]_D-26.3°. The¹H and¹³C NMR spectra were studied in detail. The values of the direct and long-range spin-spin coupling constants between the¹³C carbon nuclei and the¹H nuclei of the alkaloid molecule were measured with the aid of¹³C-[{su1}H] selective heteronuclear double resonance. The structure of 5-hydroxy-3-methyl-3-pyrrolin-2-one is suggested for lilidine.     

Macrocyclic pyrrolizidine alkaloids of crotalaria rosenii

Three macrocyclic pyrrolizidine alkaloids have been isolated from the flowers of Crotalaria rosenii. Two of them , madurensine 1 and 7-acetylmadurensine 2 are rare but known alkaloids for which full spectroscopic data have been generated and some erroneous ¹³CNMR data in the literature corrected. Crotaflorine 3, an alkaloid previously given a “probable” structure has been subjected to detailed spectroscopic analysis and shown too have structure 3. The recently introduced “COLOC” NMR technique has been used to distinguish between the two alternative structures 1 and 4.     

Entropy driven binding of the alkaloid chelerythrine to polyadenylic acid leads to spontaneous self-assembled structure formation

The binding thermodynamics and interaction of the putative anticancer alkaloid chelerythrine with polyadenylic acid were investigated by isothermal titration calorimetry, absorption and fluorescence spectroscopy, circular dichroism, differential scanning calorimetry and thermal melting experiments. The equilibrium binding constant was evaluated to be of the order of 10⁷ M⁻¹. Strong positive entropic and favorable enthalpic contributions to the binding were revealed. The binding affinity was enhanced within (10 to 100) mM Na⁺ concentration. Circular dichroism spectra confirmed that the increase in entropy change was caused by a strong conformational change in the RNA polynucleotide. Absorption and circular dichroism melting studies revealed that chelerythrine binding induced self-assembled duplex structure formation in poly(A) molecules resulting in a cooperative melting profile. This was further confirmed from differential scanning calorimetry data. The intercalation binding of the alkaloid involved strong energy transfer from the polynucleotide bases to the bound alkaloid molecules. The remarkably high entropy driven binding of the alkaloid induced spontaneous self-assembled structure formation in poly(A) and the associated binding affinity is the highest so far reported for a small molecule binding to poly(A).     

Kororamide A,a new tribrominated indole alkaloid from the Australian bryozoan Amathia tortuosa

A new tribrominated indole alkaloid, kororamide A together with the known alkaloid convolutamine F, were isolated through the application of mass directed purification from the bryozoan, Amathia tortuosa collected from northern New South Wales, Australia. The structure of kororamide A was deduced from the analysis of 1D/2D NMR and MS data. Kororamide A exists in solution as a mixture of interconverting cis–trans amide regioisomers in a ratio of 4:5. Bioactivity testing demonstrated that kororamide A was marginally active against chloroquine-sensitive and resistant strains of the malarial parasite Plasmodium falciparum, and was inactive against normal human cell lines.     

Violatinctamine, a new heterocyclic compound from the marine tunicate Cystodytes cf. violatinctus

A new alkaloid designated violatinctamine and four known metabolites were isolated from the tunicate Cystodytes cf. violatinctus collected in Kenya. Violatinctamine has a unique heterocyclic skeleton, which combines a benzothiazole unit and a dihydroisoquinoline unit. The structure of violatinctamine was elucidated by interpretation of MS results as well as 1D and 2D NMR spectra of the alkaloid and of its O,O′-dimethyl derivative. Analysis of the spectral information also implies that violatinctamine exists as a mixture of two tautomers—the imino-phenol and the amino quinone-methide.     

Alkaloids of the chinese herb guan-bai-fu ( ); guan-fu bases Y and A

A new alkaloid, guan-fu base Y,has been isolated from (Levl.)Raipaics and shown to be 2-acetoxy-14-hydroxyhetisine ( ) from its nmr (¹H, ¹³C) and mass spectra. A completed assignment of mmr peaka was made with the help of NOE and 2-D experiments which also suggest a revised structure ( ) for guan-fu baae A ( ).     

Macrodasine A, a novel macroline derivative incorporating fused spirocyclic tetrahydrofuran rings containing a spiroacetal moiety

A novel indole alkaloid, viz., macrodasine A, incorporating fused spirocyclic tetrahydrofuran rings onto a macroline-like moiety, was obtained from a Malayan Alstonia species. The structure, which is also notable for the presence of an unprecedented spiroacetal moiety in an indole alkaloid, was established by spectroscopic analysis.     

Conolutinine, a hexacyclic indole alkaloid with a novel ring system incorporating a diazaspiro center and fused oxadiazepine-tetrahydrofuran rings

A hexacyclic indole alkaloid possessing an unprecedented ring system incorporating a diazaspiro center and fused oxadiazepine-tetrahydrofuran rings has been isolated from the Malayan Tabernaemontana corymbosa. The structure was established by analysis of the spectroscopic data and a possible biogenetic pathway from a cleavamine-type precursor is presented.