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The stereochemical course of indium-promoted allylations to α-chiral aldehydes with 3-bromomethyl-5H-furan-2-one was investigated in anhydrous THF and pure H2O. High levels of 3,4-syn;4,5-syn diastereomers were produced with free hydroxyl derivatives whether in THF or pure H2O, reflecting the promising synthetic potential of this chemistry. This stereo-differentiation was attributed to the strong geometric bias exercised by our allylindium reagent and adherence to a chelation control transition-state alignment. Meanwhile, heightened levels of 3,4-anti;4,5-anti diastereomers were obtained with the rigid aldehydes 1h and 1i.

The method is extended to the preparation of (VI), the key intermediate for the synthesis of (+)-chelidonine (VII).

BACKGROUND: With the objective of exploring the herbicidal activity of substituted aurones, a series of 4,6-disubstituted and 4,5,6-trisubstituted aurones were synthesised, and their herbicidal activities against Brassica campestris L. and Echinochloa crusgalli (L.) Beauv. were evaluated in laboratory bioassays. Effects of some of the compounds were evaluated on seed germination. The most active compounds in the laboratory were evaluated in the greenhouse. RESULTS: The compounds were characterised by 1H NMR, 13C NMR and HRMS; some of them were further identified by IR. A (Z)-configuration was assigned to the aurones, based on spectroscopic and crystallographic data. Bioassay results of root growth showed that the aurones had a moderate herbicidal activity against the dicotyledonous plant Brassica campestris. (Z)-2-Phenylmethylene-4,6-dimethoxy-3(2H)-benzofuranone(6o) was the most active compound, with 81.3 and 88.5% inhibition at 10 and 100 µg ml−1 respectively, equal to the activity of mesotrione. Some of the aurones possessed some inhibition of germination on several plant species. For glasshouse tests, the substituted aurones had lower herbicidal activity than metolachlor and mesotrione. CONCLUSION: It is possible that aurone derivatives, which possess structures different from those of the commercial herbicides, may become novel lead compounds for the development of herbicides against dicotyledonous weeds with further structure modification. Copyright © 2012 Society of Chemical Industry

The method is extended to the preparation of (VI), the key intermediate for the synthesis of (+)-chelidonine (VII).

The first diastereoselective total synthesis of 8-epigrosheimin was accomplished relying entirely on substrate-controlled methods. 8-Epigrosheimin, isolated as an amoebicidal and antibiotic compound from Crepis virens, is a multi-chiral-centered guaianolide with a cis-hydroazulene and a trans-annulated γ-butyrolactone ring. Our approach featured that the γ-butyrolactone unit was formed firstly before the construction of the cycloheptane ring system. The key steps of the synthesis involved (1) a stereoselective Mukaiyama aldol addition; (2) an oxidative γ-lactonization; and (3) an intramolecular aldehyde-ene cyclization.

An efficient and diastereoselective Pd-catalyzed method of allylation of aldehydes with 3-bromomethyl-5H-furan-2-one is described. The proposed method allows the synthesis of β-(hydroxymethylaryl/alkyl)-α-methylene-γ-butyrolactones with a syn relative configuration for the first time.

An efficient and diastereoselective Pd-catalyzed method of allylation of aldehydes with 3-bromomethyl-5H-furan-2-one is described. The proposed method allows the synthesis of β-(hydroxymethylaryl/alkyl)-α-methylene-γ-butyrolactones with a syn relative configuration for the first time.

A zinc or indium-mediated Barbier-type allylation of aldehydes with 3-bromomethyl-5H-furan-2-one in aqueous solvents was developed to provide an efficient route to α-methylene-γ-butyrolactone, which is synthetically very useful. The desired products were obtained in moderate to high yields in aqueous solvents. Excellent drs were achieved, among which the best diastereomeric ratios of products were found when water was used in the indium-mediated reaction, and THF–NH4Cl (sat, aq) (2:1) mixture in the zinc-mediated reaction. Furthermore, the allylation can be induced by chiral centers, especially those in the α-position, as a substrate-controlled reaction to obtain the enantioselective homoallylation alcohols.

A Pd-catalyzed tandem ring opening—cross coupling—cyclization reaction of o-iodobenzoates (I) with azabicycle (II) is the key step in the synthesis of benzophenanthridine alkaloids like avicine (IVa), chelerythrine (IVb) or nitidine (IVc).

A highly efficient route was developed to synthesize (−)-8-epigrosheimin in four steps from aldehyde 2 based on a substrate-controlled method. The key steps of the synthesis included (1) a stereo- and regioselective allylation addition, (2) an intramolecular translactonization, and (3) an aldehyde-ene cyclization.

A zinc or indium-mediated Barbier-type allylation of aldehydes with 3-bromomethyl-5H-furan-2-one in aqueous solvents was developed to provide an efficient route to α-methylene-γ-butyrolactone, which is synthetically very useful. The desired products were obtained in moderate to high yields in aqueous solvents. Excellent drs were achieved, among which the best diastereomeric ratios of products were found when water was used in the indium-mediated reaction, and THF-NH(4)Cl (sat, aq) (2 : 1) mixture in the zinc-mediated reaction. Furthermore, the allylation can be induced by chiral centers, especially those in the α-position, as a substrate-controlled reaction to obtain the enantioselective homoallylation alcohols.

A concise and efficient synthesis of benzo[c]phenanthridines was accomplished by the palladium-catalyzed ring-opening coupling of azabicyclic alkene with o-iodobenzoates, followed by tandem cyclization. The strategy was successfully applied in the total synthesis of benzo[c]phenanthridine alkaloids such as sanguinarine, chelerythrine, nitidine and avicine.