Sorgomol, germination stimulant for root parasitic plants, produced by Sorghum bicolor

A novel strigolactone sorgomol, germination stimulant for root parasitic plants Striga and Orobanche, was isolated and structure was elucidated. Sorgomol was more active on Striga than on Orobanche and may be the immediate precursor of sorgolactone in the biosynthetic pathway of strigolactones.     

Synthetic disproof of the structure proposed for solanacol, the germination stimulant for seeds of root parasitic weeds

The structure proposed for solanacol, the germination stimulant for seeds of root parasitic weeds isolated from tobacco (Nicotiana tabacum L.), was synthesized. Comparison of the ¹H NMR data of the synthetic compounds with those reported for solanacol showed the previously proposed structure to be incorrect.     

A new efficient synthesis of GR24 and dimethyl A-ring analogues, germinating agents for seeds of the parasitic weeds Striga and Orobanche spp.

An efficient and high yielding preparation for the synthetic germination stimulant GR24 (5) and its A-ring dimethyl-substituted analogues 30-32 has been described. The first step involves a Stobbe condensation of benzaldehydes 9-11 with dimethyl succinate. Subsequent transposition of the ester and reduction of the double bond provides the building blocks 15-17 for an intramolecular Friedel-Crafts acylation. ABC-lactones 22-25 are prepared from γ-keto esters 18-21 by saponification, subsequent reduction with sodium borohydride followed by acid-catalyzed lactonization. Coupling of the lactones with the D-ring is accomplished by formylation and subsequent treatment with bromobutenolide 8 to give GR24 and its dimethyl analogues. Bioassays with Striga hermonthica seeds reveal that the dimethyl analogues are slightly less active than GR24 itself.     

A concise synthesis of (±)-pseudodeflectusin, an antitumor isochroman derivative isolated from Aspergillus sp.

A novel and concise synthesis of (±)-pseudodeflectusin (1), an antitumor isochroman derivative isolated from the culture broth of Aspergillus pseudodeflectus, was accomplished by starting from 4-(tert-butyldimethylsilyloxy)-1-pentyne (3) and diethyl 3-oxopentanedicarboxylate (5).     

First synthesis of naturally occurring (±)-epi-conocarpan

(±)-epi-Conocarpan 1 was synthesized via the key intermediate 5-bromo-cis-2-(4-methoxyphenyl)-3-methyl-2,3-dihydrobenzofuran 6 which was synthesized by a ruthenium(II) porphyrin-catalyzed intramolecular C-H insertion reaction using aryl tosylhydrazone salt 5 as the carbene source, starting from the commercially available 5-bromo-2-hydroxyacetophenone.     

Peagol and peagoldione, two new strigolactone-like metabolites isolated from pea root exudates

Two new strigolactone-like metabolites, named peagol and peagoldione, with germinative activity for root parasitic plants, were isolated from pea root exudates and were characterized by spectroscopic methods. Peagol was more active on Orobanche foetida and Phelipanche aegyptiaca seeds, while peagoldione was active on P. aegyptiaca only. Low activity was found on Orobanche crenata and Orobanche minor. Stimulatory activity of peagol on O. foetida seeds is most relevant as this species does not respond to the synthetic strigolactone analogue GR24, usually used as Orobanche germination standard.     

Total synthesis of (±)-brazilin and formal synthesis of (±)-brazilein, (±)-brazilide A using m-CPBA

Total synthesis of (±)-brazilin has been accomplished. m-CPBA epoxidation of allyl alcohol 10 and epoxy opening reaction mediated by m-chlorobenzoic acid, formed in situ as a byproduct, gave advanced intermediate diol 14. O-alkylation and cyclization gave phenol 6 which enabled the formal synthesis of (±)-brazilein and (±)-brazilide A.     

A simple and efficient total synthesis of (±)-danshexinkun A, a bioactive diterpenoid from Salvia miltiorrhiza

An efficient 12-step route for the synthesis of the diterpenoid quinone (±)-danshexinkun A in 23% overall yield from the corresponding highly substituted stilbene using a photocyclization strategy is described.     

Total synthesis of the cytotoxic cyclopeptide mollamide, isolated from the sea squirt Didemnum molle

Full details of a total synthesis of the novel reverse prenyl substituted cyclic peptide mollamide, isolated from the ascidian Didemnum molle, are described.     

Total synthesis of (±)-hyrtiazepine

The total synthesis of the azepinoindole alkaloid, (±)-hyrtiazepine, was achieved. Construction of the azepinoindole core structure was carried out by C-4 selective α-hydroxyalkylation of 5-hydroxyindole, introduction of serine at C-3 of the indole moiety, and intramolecular imination.     

Polyhydroxylated macrolide isolated from the endophytic fungus Pestalotiopsis mangiferae

A new polyhydroxylated macrolide, named mangiferaelactone (1) was isolated from a solid culture of the endophytic fungus Pestalotiopsis manguiferae, together with ten known compounds [(6S,1′S)-LL-P880α; (6S,1′S,2′R)-LL-P880β; (1′S,2′R)-LL-880γ; (1′R)-dehydropestalotin; (−)-5-carboxylmellein; (−)-5-methylmellein; (−)-5-hydroxylmethylmellein; arabenoic acid; 5,6-dihydro-4-methoxy-2H-pyran-2-one; and the (−)-2-hexylidene-3-methylsuccinic acid]. P. manguiferae was isolated from Hyptis dilatata, a small shrub common in the central region of Panama. The structure of compound 1 was elucidated by a combination of spectroscopic methods (IR, MS, optical rotation, 1D and 2D NMR spectroscopy). The absolute configuration of 1 was established as 4R,7R,8R,9S by application of vibrational circular dichroism (VCD). Compound 1 showed a minimum inhibitory concentration (MIC) of 1.6863 mg/mL against Listeria monocytogenes, and 0.5529 mg/mL against Bacillus cereus. No activity was observed for compound 1 against Plasmodium falciparum or Trypanosoma cruzi; likewise, no cytotoxic activity was observed against A2058 and H522-T1 cells.     

Total synthesis of (±)-camphorataimides and (±)-himanimides by NaBH4/Ni(OAc)2 or Zn/AcOH stereoselective reduction

Maleic anhydride 1 of Antrodia camphorate, which can be isolated from Chinese herbal medicine, is achieved in which the longest linear sequence is only five steps, in 40% overall yield from commercially available succinic anhydride. The crucial antrodimides 3 and 2 can be readily transformed by the chemoselective reduction with Zn/AcOH and NaBH₄/Ni(OAc)₂·4H₂O to afford the naturally occurring camphorataimides, 4 and 5, in high yields as well, respectively. This synthetic strategy can also be modified to give access to a variety of different maleic acid derivatives, himanimides 6-8.     

Biopreparation of an anti-inflammatory agent,diarctigenin, from arctiin isolated from Arctium lappa by Rhizoctonia solani AG-4

In the preliminary screening for the plant-derived pesticides against Rhizoctonia solani Kühn AG-4 (RS AG-4), the indicator compounds arctiin (1) and arctigenin (2) in methanol extracts of Arctium lappa L. were consumed and transformed to other compounds. Thus, in the present study RS AG-4 was used as a biocatalyst and the biotransformation of arctiin (1) was investigated. Conversion of arctiin (1) to arctigenin (2) was achieved by the enzymatic hydrolysis of sugar moiety. In addition, an anti-inflammatory lignan dimer reported from the Arctium species, diarctigenin (3) was afforded in good yields. The HPLC monitoring of the biotransformation process indicated the possible mechanism. It would be an excellent method to produce a large scale of diarctigenin (3) for the successive medicinal examinations.     

Synthetic studies on basidifferquinones: the first synthesis of (±)-basidifferquinone C

Basidifferquinones, isolated from Streptomyces sp., are potent inducers for fruiting-body formation of a basidiomycete Polyporus arcularius. Construction of the basic framework of basidifferquinones and the first synthesis of (±)-basidifferquinone C were accomplished by starting from 3,5-dihydroxy-2-naphthoic acid.     

Dihydroanthracenone metabolites from the endophytic fungus Diaporthe melonis isolated from Annona squamosa

Chemical investigation of the endophytic fungus Diaporthe melonis, isolated from Annona squamosa, yielded two new dihydroanthracenone atropodiastereomers, diaporthemins A (1) and B (2), together with the known flavomannin-6,6′-di-O-methyl ether (3). The structures of the new compounds were established on the basis of extensive 1D and 2D NMR spectroscopy, as well as by high resolution mass spectrometry and by CD spectroscopy. Compounds 1–3 were tested for their antimicrobial activity against a multi-resistant clinical isolate of Staphylococcus aureus 25697, a susceptible reference strain of S. aureus ATCC 29213 and against Streptococcus pneumoniae ATCC 49619. Compound 3 strongly inhibited S. pneumonia growth with a MIC value of 2 μg/mL, and showed moderate activity against the S. aureus multi-resistant clinical isolate and susceptible reference strain (MIC 32 μg/mL), whereas 1 and 2 were not active against the tested strains.     

Efficient construction of novel α-keto spiro ketal and the total synthesis of (±)-terreinol

The first total synthesis of (±)-terreinol is described. An intramolecular Pd(II)-catalyzed cycloisomerization of a 2-(1′-alkynyl)benzyl alcohol via an apparent 6-endo diagonal pathway led to the 1H-isochromene ring system, which was further converted to the desired spiro ketal via an iodine-mediated intramolecular spiro-cyclization.     

Improved total synthesis of (±)-trans-dihydronarciclasine, devised for large-scale preparation

New synthetic route to (±)-trans-dihydronarciclasine, more suitable for a large-scale preparation, has been devised with the early stage incorporation of ester functionality for direct assembly of the B-ring lactam.     

Formal total synthesis of (±)-magellanine

Formal total synthesis of magellanine is described. Key features in the synthesis were stereoselective Ireland-Claisen rearrangement and intramolecular Pauson-Khand reaction of exo-cyclic enynes.     

Total synthesis of (±)-megistophylline I

(±)-Megistophylline I (1), carrying a dienone residue in the acridone framework, was synthesized using the Claisen rearrangement to introduce a prenyl group as a key step.     

N,N′-Diisopropyl- and N,N′-dicyclohexylthiourea cadmium(II) complexes as precursors for the synthesis of CdS nanoparticles

Crystals of the cadmium(II) complexes of N,N-diisopropylthiourea and N,N-dicyclohexylthiourea were obtained and their X-ray single crystal structures determined. These complexes are air-stable, easy to prepare and inexpensive and decompose cleanly to give good quality crystalline CdS. The nanoparticles of CdS thus obtained showed quantum confinement effects in their optical spectra, with close to band-edge emission in luminescence experiments. The broad diffraction patterns observed are typical of nanodimensional particles. The variation of concentration of precursor-to-HDA ratio change the isolated materials from spheres to rod-shaped. TEM images showed agglomerates of needle-like plate of particles.