Chinese Journal of Chemistry

The cover picture shows a concise total synthesis of amphidinin B, a polyketide metabolite isolated from the extracts of cultured marine dinoflagellates Amphidinium sp. (Y-56 strain). By playing a ring-forming trick, selective oxidative cleavage at the two monosubstituted alkene sites was achieved in the presence of the 1,1-disubstituted counterpart. Thus, starting from the triene precursor a ring-closing metathesis (RCM) reaction was performed to form the (12E)- and (12Z)-cycloalkenes. The latter were then subjected to regio- and stereoselective asymmetric dihydroxylation (AD), respectively, to produce the 12,13-diols. Further oxidative cleavage of the diols furnished amphidinin B. More details are discussed in the article by Dai et al. on page 105–110.

Starting from the known (S)-carvone, we have achieved the synthesis of the advanced intermediate 6 in 17 steps with an overall yield of 3.9%, which led to a formal total synthesis of 9-deoxygelsemide.

Curcuphenol is an interesting terpenoid with diverse bioactivities. We report an expedient asymmetric synthesis of curcuphenol from citronellal which features only two purification operations in the overall six-step synthesis.

A method for the efficient and reliable synthesis of aryl nitriles via the Cu₂O-catalyed cross-coupling of aryl boronic acids or esters and TMSCN is presented. The room temperature operation paired with the use of cheap, readily available, and halogen-free Cu₂O as catalysts makes the protocol an appealing option for aryl cyanations.

An efficient semi-synthetic method was developed to construct docetaxel 1 by using N,N-di-Boc protected linear isoserine derivative 5 as the side chain source.

A range of β-keto acids smoothly undergo decarboxylative alkylation with isochromans in the presence of 2,2,6,6-tetramethylpiperdine-1-oxoammonium hexafluorophosphate to give structurally diverse 1-acylmethylisochromans in moderate to excellent yields.

The total synthesis of tubulysin V was accomplished in 1.0% overall yield with linear 13 steps. Our synthetic strategy featured the following two reactions. One is zinc-mediated aza-Barbier reaction of (R)-N-tert-butanesulfinyl imine 8 with β-ester group functionalized allylic bromide 9 to afford the chiral homo-allylic amine 7; the other is to employ the methodology of aqueous indium-mediated aza-Barbier reaction previously developed by our group, giving the chiral homo-allylic amine 13 with high efficiency.

Completely anti-diastereoselective: This can be achieved by using bromine atom as a traceless directing group in the SmI₂-mediated reductive coupling of α,β-unsaturated ester with ketones; or by the one-pot reaction of the organozinc reagent generated from bromomethacrylate with ketone. On the basis of these results, two approaches to the spirolactone moiety with anti-configuration (C-9/C-9a) found in some Stemona alkaloids were disclosed.

A key intermediate, 6,19-dihydroxyandrostenedione, was successfully prepared in six steps from commercially available raw material. The process can be carried out on a large scale without laborious chromatography.

Dinuclear Mg complexes generated in situ from the combination of phenol-bridged bis(α,α-diarylprolinol) ligands and n-Bu₂Mg were found to be efficient for the catalytic asymmetric ring opening of meso-epoxides with aniline derivatives as nucleophiles, affording the corresponding chiral β-amino alcohols in good yields with up to 90% ee.

Six new mexicanolide-type limonoids, dysoxylumasins A–F (1–6) together with eight known compounds, were isolated from the leaves and twigs of Dysoxylum mollissimum Bl. Their structures were established by the analyses of spectroscopic data.

Starting from alcohol (2), and on the basis of Yamamoto rearrangement, intramolecular cyclopropanation reaction, 1,3-dipolar cyclization, and intramolecular Heck reaction, the Lindenane-type sesquiterpenoid fragement (20) of Chlorahololide A (1) has been synthesized in a linear sequence of 21 steps and an overall yield of 1.8%. The flexible synthetic route could generate further natural products of the Chloranthaceae family.

Natural product mayamycin is the first example in the angucycline class featuring a C-glycoside linkage at the C5-position of the benz[a]anthracenone core with remarkable biological activities. We successfully synthesized the two retrosynthetic fragments, but the final C-glycosylation did not occur. Instead, a two-ring less analog was success fully prepared, suggesting the steric effect played an important role in the synthesis of mayamycin.

The ester-linked triene I, designed for synthesis of 19-membered amphidinolide T1 and T3–T5 via the cycloalkene (12E)-II, has now been transformed into amphidinin B from both (12E)- and (12Z)-II through oxidative cleavage and subsequent oxidation.

A chiral acetal-enabled and SnCl₄-promoted biomimetic polyene cationic cyclization was followed by oxidation and a cascade process of Birch reduction and alkylation to complete a core skeleton of representative ent-kaurene diterpenoids.

A series of A-B type sterically regular bicyclio[3.3.0] diene-based polymers were designed and synthesized as immobilized chiral diene ligands for asymmetric catalysis. By using polymeric diene, good to excellent enantioselectivities can be achieved in Rh-catalyzed asymmetric 1,4-addition of arylboronic acids to α,β-unsaturated ketones.

First total synthesis of the proposed structures of β-indoloquinazoline alkaloids orisuaveolines A and B is reported. The key steps of the synthesis included a Pictet-Spengler reaction to build a six-member lactam which further transformed into target molecular by a one-pot condensation. The structures of our synthesized products were confirmed by 2D-NMR experiments.

Biotransformation of tigogenin-derived pregnane-3β,16β,20-triol (1) by Cunninghamella echinulata produced four new highly oxidized C₂₁-steroids, pregnane-3β,14α,16β,20-tetrol (2), pregnane-3-oxo-14α,16β,20-triol (3), pregnane-3-oxo-7β,16β,20-triol (4), and pregnane-3β,7β,16β,20-tetrol (5).

A Pd(II)-catalyzed oxidative cyclization of olefinic tosylamides was developed for the preparation of aryl-fused and N-containing six-membered heterocycles. Under optimized conditions the reaction proceeded with high activity and selectivity, with yields of up to 83% being obtained. This procedure provides a facile and efficient route to the aforementioned heterocycles with 2-acetoxy functionality.

Conversion of dihydroqinghao acid into natural arteannuin O was achieved via sequential oxidative lactonization, epoxidation, perhydrolysis of the expoxy ring and dimethyl sulfide reduction of the peroxyl group.

3-Aryl-1,2,4-benzotriazines were conveniently prepared in moderate to good yields from 1,l-bis(benzotriazol-1-yl) methylarenes with allylsamarium bromide/hexamethyl-phosphramide (allylSmBr/HMPA). Preliminary results indicate that HMPA has the potential to enhance the reducing ability as well as to prohibit the nucleophicility of allylSmBr, thus making allylSmBr/HMPA as a promising single-electron transfer (SET) reagent.

Concise and efficient syntheses of (−)-chloramphenicol, (+)-thiamphenicol and (+)-sphinganine have been accomplished in practical four or three steps. The synthetic route featured in an aldol reaction between iminolactone 1a and 1b with aldehyde, which introduced the two continuous chiral centers within three target molecules.

A series of new platinum(II) complexes with C₂-asymmetric and C₂-symmetric 1,2-diamines were designed and synthesized by convenient methods, involving samarium diiodide induced reductive coupling as the key step. The cytotoxicity of these analogs against four leukemia and three solid cancer cell lines was evaluated and the preliminary structure-activity relationship is also discussed. Flow cytometry data indicated that (R,R)-11a could obviously arrest leukemia K562 cells in G2/M phases.