Total synthesis of the Fusarium toxin equisetin

A short stereoselective synthesis of the Fusarium toxin equisetin, a potent inhibitor of HIV-1 integrase enzyme is described, using as the key step a stereoselective intramolecular Diels-Alder reaction of a fully conjugated E,E,E-triene with a trisubstituted gamma,delta-unsaturated beta-ketothioester.     

The Stereoselective Synthesis of Disubstituted E,Z-Diene Ester

The new method for the stereoselective synthesis of disubstituted diene ester was successfully applied to a highly stereoselective synthesis of E, Z-diene ester (1).     

Highly stereoselective synthesis of (2E,4E)-dienamides and (2E,4E)-dienoates via a double elimination reaction

Highly stereoselective synthesis of (2E,4E)-dienamides and (2E,4E)-dienoates was achieved through a double elimination reaction of β-acetoxy sulfones.     

Stereoselective preparation of dienol phosphates from alpha,beta-ethylenic aldehydes

The first stereoselective method of preparation of (E)-dienol phosphates from alpha,beta-ethylenic aldehydes is described. The key point is the stereoselective enolization of conjugated alkenals by potassium tert-butoxide in the presence of N-methylpyrrolidinone (NMP).     

Expedient stereoselective synthesis of coronafacic acid through intramolecular Diels-Alder cyclization

A stereoselective synthesis of coronafacic acid, a natural component of the phytotoxin coronatin, was achieved using an intramolecular Diels-Alder reaction as the key step. The triene precursor bearing a substituted diene and a vinylketone as dienophile was synthesized and then tested in the thermal intramolecular cyclization. We have devised a new strategy to assemble the E,Z-diene through the stereoselective aldol reaction of an ester enolate followed by a stereoselective dehydration. Following the thermal cyclization, the corresponding hydrindanone thereby obtained with the desired relative stereochemistry could easily be converted into the natural product. The synthesis of the coronafacic acid was accomplished in six steps in 29% overall yield.     

Synthetic studies on azadirachtin: stereoselective construction of the ABCE ring system

A new method for constructing the ABCE ring system of azadirachtin in a stereoselective manner was developed. The synthesis of the model compound features (1) stereoselective construction of the highly hindered C8 quaternary center by an intermolecular addition reaction of an allylborane with an aldehyde and (2) construction of the E ring moiety by the Pd-catalyzed Nazarov cyclization.     

Synthesis and reactivity of E,Z butadiene-iron tricarbonyl complexes.

The synthesis, structure and thermal stability of the E,Z butadiene-iron tricarbonyl complex 1 is reported. This complex reacts with organometallic nucleophiles in a stereoselective synthesis of functionalized E,Z dienes.     

Stereoselective synthesis of conjugated all-trans-tetraenes. Application to the synthesis of β-parinaric acid methyl ester

in this paper is reported the stereoselective synthesis of all-trans-tetraenes by reductive elimination of 1,8-dibenzoate-2,4,6-trienes with sodium amalgam. The method was applied to the syntheses of 4E, 6E, 8E, 10E-heptatetraene and β—parinaric acid methyl ester.     

A highly stereoselective, modular route to (E)-vinylsulfones and to (Z)- and (E)-alkenes

A recently discovered radical fragmentation of 2-fluoro-6-pyridinoxy derivatives allows a new highly stereoselective and convergent route to (E)-vinylsulfones from allylic alcohols. Reductive desulfonylation or nickel-catalyzed couplings furnish di- and trisubstituted (E)- and (Z)-alkenes.     

Stereoselective synthesis of trisubstituted olefins by a directed allylic substitution strategy

New methodology for the stereoselective synthesis of trisubstituted olefins is presented. The use of ortho-diphenylphosphanyl benzoate (o-DPPB) as a directing leaving group for copper-mediated allylic substitution with Grignard reagents allowed for the stereoselective construction of a wide range of E olefins, without the need for an adjacent electron-withdrawing group. Our modular three-step approach toward trisubstituted alkenes commenced with geminal α-methylene aldehydes. Addition of an organometallic reagent and introduction of the o-DPPB group by esterification was followed by the o-DPPB-directed copper-mediated allylic substitution with a Grignard reagent to furnish stereodefined trisubstituted olefins. Additionally, incorporation of a stereocenter from the chiral pool allowed the preparation of an enantiomerically pure olefin that bore three alkyl substituents in high E/Z selectivity.     

Single-isomer trisubstituted olefins from a novel reaction of (E)-beta-chloro-alpha-iodo-alpha,beta-unsaturated esters and amides

(E)-beta-chloro-alpha-iodo-alpha,beta-unsaturated esters are converted to single isomer trisubstituted olefins bearing three different carbon substituents by cross-coupling under reflux. Mechanistic investigations suggest that this process transfers a hydrogen from the boronic acid to the alpha-position of the substrate and then introduces an aryl group to the beta-position of the intermediate template while replacing chloride. The reaction is highly stereoselective, showing preference for the E-isomer. The process proceeds through (E)-beta-chloro-alpha-aryl-alpha,beta-unsaturated esters that are transformed efficiently into the corresponding E-products through stereoselective Suzuki-type reactions giving single isomers. The observed stereochemistry is apparently enabled by the intermediacy of a palladium allenoate. The reaction involves a catalytic cycle in which Pd(II) is reduced to Pd(0) through the formation of biaryl-coupled products.     

Sulfur dioxide-mediated syntheses of polyfunctional alkenes and (E,Z)- and (E,E)-2,4-dien-1-ones

Efficient methods for the stereoselective synthesis of polyfunctional (E)- and (Z)-alkenes and conjugated (E,E)- and (E,Z)-dienones are presented. They rely upon one-pot, four-component processes that condense 1-oxy-1,3-dienes, silyl enol ethers, SO2, and carbon electrophiles. [structure: see text]     

Total synthesis of (+)-crocacin C

The first asymmetric synthesis of (+)-crocacin C (3) is described which served to confirm the absolute configuration of this compound. The key step in the sequence was the stereoselective assembly of the (E,E)-diene amide side chain by a Stille cross-coupling between the stannane 5 and vinyl iodide 6.     

A stereoselective synthesis of (+/-)-C-secolimonoid BCDE model compounds related to the insect antifeedant ohchinolide.

A short and stereoselective synthesis of a (+/-)-BCDE C-secolimonid model insect antifeedant related to ohchinolide and nimbolidin was accomplished in 13 (30% overall yield) and 15 (30% overall yield) steps, respectively, from ethyl drimanate. The key steps are the torquoselective electrocyclization of the divinyl ketone 6, induced by perchloric acid, and the stereoselective rearrangement of the hydroxy lactone 12, inspired in a biosynthetic proposal. An alternative route, which provides access to (+/-)-BCDE ohchinolide and nimbolidin isomers, is also described.     

E -型α, β-不饱和酰胺的立体选择合成

本文报道了在钯及二丁基碲存在下, 溴代乙酰胺与醛的亲卤缩合反应, 提供了E型α, β-不饱和酰胺的立体选择合成。     

Regio- and stereoselective synthesis of novel (E)-1-alkenyl carbamate via carbocupration reaction

The stereoselective carbocupration and copper-catalyzed carbomagnesiation reactions of alkynyl carbamates are described as a new and straightforward method for the preparation of (E)-alkenyl enol carbamates. [reaction: see text]     

Stereoselective formation of N-acyliminium ion via chiral N,O-acetal TMS ether and its application to the synthesis of beta-amino acids

[reaction: see text] The highly stereoselective synthesis of beta-amino acids via the chiral 4-phenyloxazolidinone-controlled linear N-acyliminium ion reaction has been achieved by employing chiral N,O-acetal TMS ethers. In addition, the mechanism of the excellent stereochemical outcome has been elucidated. The oxazolidinone auxiliary plays a dual role in stereocontrol: the E/Z geometry control of the N-acyliminium ion induced by an initial stereoselective amide reduction, leading to the chiral N,O-acetal TMS ether, and face control of the nucleophile attack in the N-acyliminium ion reaction.     

Total synthesis of the anticancer natural product OSW-1

The highly potent anticancer natural saponin OSW-1 has been successfully synthesized from commercially available 5-androsten-3beta-ol-17-one 79 in 10 operations with 28% overall yield. The key steps in the total synthesis included a highly regio- and stereoselective selenium dioxide-mediated allylic oxidation of 80 and a highly stereoselective 1,4-addition of alpha-alkoxy vinyl cuprates 68 to steroid 17(20)-en-16-one 12E to introduce the steroid side chain. This total synthesis demonstrated once again the versatile synthetic applications of alpha-halo vinyl ether chemistry developed in our laboratories.     

A Novel Approach to the Stereoselective Synthesis of (E)-1-(1-Alkenyl)Benzotriazoles

The Horner-Wadsworth-Emmons olefination of diethyl-(1-benzotri-azolmethyl)phosphonate by means of aldehydes was found to be a convenient method for the stereoselective preparation of (E)-1-(1-Alkenyl)benzotriazoles.     

Synthetic study of macquarimicins: highly stereoselective construction of the AB-ring system

The highly stereoselective synthesis of the AB-ring system of macquarimicins, a novel class of microbial metabolites with inhibitory activity for neutral sphingomyelinase, has been achieved. The present synthesis features the highly stereocontrolled construction of the cis-tetrahydroindan structure via the intramolecular Diels-Alder reaction of an (E,Z,E)-1,6,8-nonatriene derived from D-glyceraldehyde acetonide. Reaction: see text.