Total synthesis of the indole alkaloids henrycinol A and B

The total synthesis of new indole alkaloids henrycinol A and B were accomplished starting from l-tryptophan methyl ester. The key step is a stereochemically flexible Pictet–Spengler reaction governed by the presence or absence of an N-allyl group in the tryptophan precursor. The natural products henrycinol A and B were synthesized in good overall yield in eight and nine steps, respectively.     

Calyciphyllines A and B,two novel hexacyclic alkaloids from Daphniphyllum calycinum

[structure: see text] Two types of Daphniphyllum alkaloids with unprecedented fused-hexacyclic ring systems, calyciphyllines A (1) and B (2), have been isolated from the leaves of Daphniphyllum calycinum (Daphniphyllaceae), and the structures and relative stereochemistry were elucidated on the basis of spectroscopic data.     

Meloslines A and B,two novel indole alkaloids from Alstonia scholaris

An unprecedented indole alkaloid melosline A (1), with 6/5/6/6 tetracyclic ring skeleton, together with a new alkaloid melosline B (2) and one known compound (3) were isolated from the leaves and twigs of Alstonia scholaris. The new structures were elucidated by comprehensive spectroscopic analysis. The absolute configuration of compound 1 was confirmed by comparison of experimental data with calculated electronic circular dichroism (ECD). Compound 1 exhibited moderate cytotoxicity against MCF-7 cancer cell lines.     

Total synthesis of dl-asparenomycins A,B and C,novel carbapenem antibiotics

Total synthesis of dl-asparenomycins was accomplished with direct conversion of carbonates 13a, 13b and 14a, 14b to asparenomycin esters 15 and 16 and carboxy deprotection by the AlCl₃-anisole method.     

Aminocadambines A and B, two novel indole alkaloids from Neolamarckia cadamba

Two novel monoterpenoid indole alkaloids, aminocadambines A (1) and B (2), characterized by tetrahydrofuran and 1,2,3,4-tetrahydropyridine rings, were isolated from the leaves of Neolamarckia cadamba. Their structures were elucidated on the basis of spectroscopic and computational methods. The absolute configuration of 1 was established by CD analysis. A plausible biosynthetic pathway for 1 and 2 is proposed.     

Daphlongeranines A and B, two novel alkaloids possessing unprecedented skeletons from Daphniphyllum longeracemosum

Two novel alkaloids, daphlongeranines A (1) and B (2), with an unprecedented ring system, were isolated from the fruits of Daphniphyllum longeracemosum. Their unique structures and relative stereochemistries were established on the basis of spectroscopic and single-crystal diffraction analysis. The proposed biosynthetic pathway was also discussed. Compounds 1 and 2 showed weak inhibition on platelet aggregation.     

Flueggenines A and B, two novel C,C-linked dimeric indolizidine alkaloids from Flueggea virosa

[structure: see text] Two unprecedented C,C-linked dimeric indolizidine alkaloids, flueggenines A (1) and B (2), as well as their biosynthetic precursor (-)-norsecurinine, were isolated from the roots of Flueggea virosa. Their structures and absolute configurations were elucidated by spectroscopic methods, especially 2D NMR and CD spectral analyses, and supported by their unique biosynthetic pathway as proposed. Both 1 and 2 were tested against two tumor cell lines, and alkaloid 1 showed weak activity against the P-388 cell line.     

Total synthesis of the novel angiogenesis inhibitors epoxyquinols A and B

The synthesis of the recently discovered angiogenesis inhibitors epoxyquinols A and B, having novel polyketide derived dimeric structures, has been accomplished from the readily available Diels-Alder adduct of cyclopentadiene and p-benzoquinone through a short, simple and flexible strategy that is diversity oriented and can be adapted to an asymmetric variant.     

Trigonoines A and B, two novel alkaloids from the leaves of Trigonostemon lii

Two novel alkaloids, trigonoine A containing a 2,8-diazabicyclo[3.3.1]nonane ring system and trigonoine B formed by a combination of a 2,3-dihydroquinolin-4-one and 3H-pyrrolo[2,3-c]quinoline rearranged from β-carboline skeleton were isolated from the leaves of Trigonostemon lii. Their structures were elucidated by 1D and 2D NMR spectroscopic methods.     

Total synthesis of carbazole alkaloids

A Suzuki-Miyaura cross coupling, followed by triphenylphosphine mediated Cadogan reductive cyclization sequence provided efficient access to a series of carbazole alkaloids.In the present work, this approach was applied to the total synthesis of mukonine, clauszoline K, koenoline, murrayanine, murrayafoline A, mukoeic acid, glycoborine, glycozolicine, mukolidine, mukoline, glycozoline, 3-methoxy-9H-carbazole-1-carboxylic acid methyl ester, (3-methoxy-9H-carbazol-1-yl)-methanol, 3-methoxy-9H-carbazole-1-carbaldehyde, 3-methoxy-9H-carbazole-1-carboxylic acid, 2-methyl-9H-carbazole and nonsteroidal anti-inflammatory drug (NSAID) carprofen and its derivatives.     

A novel total synthesis of elaeocarpus alkaloids

The novel synthesis of elaeocarpus alkaloids has been achieved employing 1,3-dipolar cycloaddition reaction as a key step.     

Total synthesis of marine bisindole alkaloids, (+)-hamacanthins A, B and (−)-antipode of cis-dihydrohamacanthin B

The total synthesis of the marine bisindole alkaloids, (+)-hamacanthins A (2a) and B (2b), and (−)-antipode of cis-dihydrohamacanthin B (2e) was achieved by transamidation-cyclization of N-(2-aminoethyl)-2-oxoethanamide 18 derived from (S)-indolylglycinol 10.     

Total synthesis of mauritines A, B, C, and F: cyclopeptide alkaloids with a 14-membered paracyclophane unit

A unified strategy for the synthesis of mauritines A (5), B (6), C (7), and F (10) has been developed based on a key intramolecular nucleophilic aromatic substitution reaction (S(N)Ar) for the formation of the strained 14-membered paracyclophane. It was demonstrated that the outcome of the cycloetherification is independent of the stereochemistry of the peptide backbone and that both (1R)-16 and (1S)-16 cyclized smoothly to provide the corresponding macrocycle. On the other hand, dehydration of the secondary benzylic alcohol, via the phenylselenide intermediate, is configuration dependent. (1R)-25 underwent the two-step syn-elimination much more easily than (1S)-22. A modified reductive deamination procedure via the diazonium intermediate was developed. A complete assignment of proton and carbon NMR spectroscopy signals for these natural products is reported for the first time.     

Total synthesis of monoterpenoid isoquinoline alkaloids

A novel analogue (3) of dihydrosecologanin aglucone has been synthesised via a substituted cyclopentenolone and converted into (±)-protoemetine (10) and related Ipecac alkaloids.     

Manzamine B and C,two novel alkaloids from the sponge haliclona sp.

The title compounds were isolated from a marine sponge collected off Okinawa. Their structures were determined by X-ray and shown to be 1-β-carbolines. Manzamine C was the 2-ethyl-N-azacycloundec-6-ene derivative, whereas manzamine B was more complex being the epoxy isomer of the free base of dihydromanzamine A.     

Concise synthesis of quinazoline alkaloids, luotonins A and B, and rutaecarpine

The total synthesis of luotonin A was achieved in excellent yield by using a Pd-assisted biaryl coupling reaction of N-(bromoquinolinyl)methylquinazolinone with Cy₃P and KOAc. The successive treatment of luotonin A with NBS and aq. AgNO₃ gave luotonin B in good yield. Although the Pd-assisted coupling reaction of N-(2-bromoindolyl)ethylquinazolinone with Cy₃P and KOAc yielded rutaecarpine in poor yield, N-acetate under the same reaction conditions yielded the desired rutaecarpine directly in excellent yield.     

Cassiarins A and B, novel antiplasmodial alkaloids from Cassia siamea

Two novel alkaloids with an unprecedented tricyclic skeleton, cassiarins A (1) and B (2), have been isolated from the leaves of Cassia siamea, and the structures were elucidated on the basis of spectroscopic data. Cassiarin A (1) showed a potent antiplasmodial activity.     

Kopsihainanines A and B, two unusual alkaloids from Kopsia hainanensis

Kopsihainanine A (1), an unprecedented skeleton with a 6/5/6/6/6 pentacyclic rearranged ring system, together with a new biogenetically related compound, kopsihainanine B (2), were isolated from Kopsia hainanensis. Their structures were elucidated by means of spectroscopic methods. The absolute configuration of 1 was determined by ECD calculation.