Stereocontrolled synthesis of onchidins

[structure: see text] The first total synthesis of a molecule possessing the stereochemistry proposed for onchidin is described. The structure synthesized appears to be different from that of the marine natural product.     

Stereocontrolled synthesis of dihydropseudoclovene-B

Aryl participated intramolecular cyclisation of the bromophenol 16 yielded the dienone 17 which was converted into dihydropseudoclovene-B (7) via a stereocontrolled route.     

Stereocontrolled total synthesis of pancratistatin

A new total synthesis of the antitumor alkaloids, pancratistatin (1), has been accomplished from readily available staring materials. The Claisen rearrangement of dihydropyranethylene 5 was employed to construct the A and C rings. Stereo- and regiocontrolled functional group interchange, such as iodolactonization, dihydroxylations, and a cyclic sulfate elimination reaction, allows for the production of the target natural product. [reaction: see text]     

Stereocontrolled synthesis of (+)-boronolide

Boronolide was synthesized stereoselectively from hydroxyacetylfuran 5 and valeraldehyde 6 using a novel dizinc aldol catalyst. Ring closing metathesis provides the lactone ring. The synthesis requires 12 steps and proceeds in 26% overall yield. [reaction: see text]     

Stereocontrolled synthesis of lepadiformine A

In this paper we present results of a study into whether the tricyclic core of the lepadiformines A-C can be accessed via intramolecular hetero-Diels-Alder cycloaddition. We are able to demonstrate that such a process is possible and that the reaction proceeds in an endo-selective fashion, providing the correct relative stereochemistry for this family of natural products. By employing this approach we have been able to develop a short (7 step) synthesis of (+/-)-lepadiformine A, starting from commercially-available trans-2-nonenal.     

Stereocontrolled total synthesis of (+)-pederine

A mild one-pot method for the synthesis of acyclic N-(1-methoxyalkyl)amides starting from carboxylic acid and methyl imidates has been developed and applied to the first total synthesis of (+)-pederine (1), a potent insect poison. Furthermore, the stereocontrolled total synthesis of 1 was also achieved by employing acid catalyzed double alkoxy-exchange reaction of N-(1 -methoxylakyl)amide group as key step.     

Stereocontrolled synthesis of ara-type cyclohexenyl nucleosides

A highly stereocontrolled synthesis of a new class of carbocyclic nucleosides, ara-type cyclohexenyl nucleosides, was developed. The key intermediate (+/-)-9 was obtained after a series of transformations starting from easily available endo-bicyclo carboxylic acid (+/-)-3. The allylic hydroxyl group of (+/-)-9 was masked via oxidation with manganese dioxide and released, after protection of the 2'-hydroxyl group, via reduction with NaBH(4) in the presence of CeCl(3).7H(2)O. The base moiety was introduced with use of the Mitsunobu methodology.     

Stereocontrolled synthesis of quinine and quinidine

Disubstituted cyclopentene was prepared from cyclopentene monoacetate and transferred into disubstituted piperidine via oxidative cleavage of the olefin moiety followed by piperidine ring formation. The piperidine was then condensed at the side chain with a quinoline part to afford the olefin precursor of quinine. Finally, the olefin was converted into quinine through the corresponding epoxide. Quinidine was synthesized in a similar way.     

Stereocontrolled total synthesis of isocomene sesquiterpenes

Four isomers of the sesquiterpene isocomene have been synthesized in high yields and in a stereocontrolled fashion from the tricyclic triquinane 1 obtained by the cyclopentene annulation method. Carbon-13 data was obtained for all of the isocomene sesquiterpenes.     

Stereocontrolled total synthesis of (+)-vinblastine

A stereocontrolled total synthesis of (+)-vinblastine was accomplished, featuring preparations of the two indole units by means of a novel indole synthesis via radical cyclization of thioanilide, and a stereoselective coupling of these units.     

Stereocontrolled synthesis of 2,3-anhydro-beta-d-lyxofuranosyl glycosides

[reaction: see text] The stereocontrolled synthesis of 2,3-anhydro-beta-D-lyxofuranosyl glycosides from thioglycoside 2 and glycosyl sulfoxide 3 is reported.     

Stereocontrolled synthesis of highly functionalized spirocyclic pyrans

Highly functionalized spirocyclic pyrans can be obtained through the Achmatowicz rearrangement of furyl carbinols by taking advantage of the different rates of reaction for epoxidation and nucleophilic addition. Through this methodology, spirocyclic units of various ring sizes can be selectively generated with complete stereocontrol.     

Stereocontrolled synthesis of methyl silanediol peptide mimics

The treatment of chiral sulfinimines with (methyldiphenylsilyl)lithium gives alpha-(methyldiphenylsilyl)sulfinamides with excellent diastereoselectivity, and in good yield. The presence of alpha-protons on the imines is also well tolerated. The sulfinamide auxiliary is easily removed via treatment with methanolic HCl and the resulting amine extended into peptide chains accordingly. The diphenylsilyl moiety is a resilient protecting group for the corresponding silanediol, which can be unmasked via treatment with TfOH, followed by aqueous hydrolysis. The crude silanediol may be isolated and purified as its corresponding bis-TMS siloxane via protection with TMSCl, and converted back to the desired silanediol via hydrolysis with aqueous KOH. Efforts to apply this approach to biologically relevant silanediol peptide mimics, with a view to protease inhibition, are described.     

Stereocontrolled chemoenzymatic synthesis of 2,3-disubstituted piperidines

(R,R)-2,3-Disubstituted piperidines were readily synthesized starting from (R)-(+)-5-bromo-2-hydroxypentanenitrile (R)-2. An enantioselective (R)-oxynitrilase-catalyzed transcyanation was used to prepare the starting cyanohydrin (R)-2.     

含手性磷酸酯基的寡核苷酸类似物的立体控制性合成

本文总结了近十几年来立体控制性合成含手性磷酸酯基的寡核苷酸类似物的进展, 重点介绍了寡核苷酸硫代磷酸酯和甲基膦酸酯的立体控制性合成方法 .     

Stereocontrolled synthesis of the histrionicotoxin ring system

Two simple, efficient and stereocontrolled routes to the $\text{cis}$-azaspiro-[5-5]-undecan-8-ol skeleton of the histrionicotoxin alkaloids are described.     

Stereocontrolled synthesis of (-)-galanthamine

An enantioselective synthesis of (-)-galanthamine has been realized in 11 linear steps starting from isovanillin. A Mitsunobu aryl ether forming reaction was used to assemble the galanthamine backbone, which was stitched together using enyne ring-closing metathesis, Heck, and N-alkylation reactions affording the tetracyclic ring system. Control of relative and absolute stereochemistry was derived from an easily accessible enantiomerically enriched propargylic alcohol 13.