A concise stereoselective synthesis of (-)-erycibelline

(-)-Erycibelline, the dihydroxynortropane alkaloid isolated from Erycibe elliptilimba Merr. et Chun., was synthesized using a cyclic nitrone as advanced intermediate, wherein the key step was the SmI(2)-induced intramolecular reductive coupling of cyclic nitrone with aldehyde which resulted in good yield and stereoselectivity.     

A concise asymmetric synthesis of (-)-rasfonin

A very efficient total synthesis of the apoptosis inducer (-)-rasfonin has been developed using CuBr/JosiPhos catalyzed iterative asymmetric conjugate addition of MeMgBr and Feringa's butenolide.     

A concise and efficient synthesis of vildagliptin

An original synthesis of vildagliptin ((S)-1-[2-(3-hydroxyadamantan-1-ylamino)acetyl]pyrrolidine-2-carbonitrile), a powerful DPP-4 inhibitor, was developed. Vildagliptin was assembled from 3-amino-1-adamantanol, glyoxylic acid and l-prolinamide in a 4-step reaction sequence with the isolation of only two intermediates. The procedure is competitive with existing protocols, leading to vildagliptin in 63% overall yield.     

A concise total synthesis of (-)-maoecrystal Z

The first total synthesis of (-)-maoecrystal Z is described. The key steps of the synthesis include a diastereoselective Ti(III)-mediated reductive epoxide coupling reaction and a diastereoselective Sm(II)-mediated reductive cascade cyclization reaction. These transformations enabled the preparation of (-)-maoecrystal Z in only 12 steps from (-)-γ-cyclogeraniol.     

A concise synthesis of (±)-3-deoxyisoaltholactone

The novel styryl lactone analog (±)-3-deoxyisoaltholactone was synthesized in 5 steps from dihydrofuran. An intramolecular vinylsilane–oxocarbenium condensation thus afforded the central cis-fused bicyclic ether array in near quantitative yield as a single stereoisomer.     

A concise synthesis of (+/-)-cacalol

A simple synthesis of the natural product cacalol has been developed that proceeds in seven steps and 21-25% overall yield. Ortho-lithiation of 4-methylanisole and alkylation with 5-iodo-1-pentene, followed by intramolecular Friedel-Crafts alkylation, gave 5-methoxy-1,8-dimethyltetralin. This compound was then formylated in the 6-position. Baeyer-Villiger oxidation and hydrolysis of the resulting formate gave 6-hydroxy-5-methoxy-1,8-dimethyltetralin. Alkylation of the phenolic hydroxyl group with chloroacetone followed by cyclodehydration gave cacalol methyl ether. Deprotection of this aryl methyl ether yielded cacalol.     

A concise total synthesis of (+/-)-1-epiaustraline

[reaction: see text] A concise total synthesis of 1-epiaustraline 3 is described that utilizes a diastereoselective Birch reduction of an electron-deficient pyrrole and a chelation-controlled vinyl Grignard addition to an aldehyde to introduce the C7 stereocenter. The C1 and C2 stereocenters were set through an OsO(4)-catalyzed dihydroxylation.     

A concise and stereoselective synthesis of (+)- and (−)-deoxoprosophylline

An efficient synthesis of (+)- and (−)-deoxoprosophylline was accomplished from the readily available cis-2-butene-1,4-diol in which the Sharpless asymmetric dihydroxylation was used as the key step.     

A concise synthesis of (S)-N-ethoxycarbonyl-alpha-methylvaline

A practical and efficient protocol for the three-step synthesis of (S)-N-ethoxycarbonyl-alpha-methylvaline 3 is described which utilizes readily available commercial starting materials. The key transformations involve resolution-crystallization of tartrate salt 6 followed by a one-pot procedure for the preparation of 3 which is isolated as the dicyclohexylamine salt in 45% overall yield and in 91-95% ee.     

A concise synthesis of diethyl 1-(tert-butoxycarbonylamino)-1-alkenylphosphonates

An efficient completely diastereoselective synthesis of (Z)- and (E)- N-Boc 1-aminoalkenylphosphonic acid diethyl esters from easily available 5-substituted (2-thioxo-oxazolidin-4-yl)phosphonic acid diethyl esters has been developed.     

Development of a concise synthesis of (-)-oseltamivir (Tamiflu)

We report a full account of our work towards the development of an eight‐step synthesis of anti‐influenza drug (?)‐oseltamivir (Tamiflu) from commercially available starting materials. The final synthetic route proceeds with an overall yield of 30 %. Key transformations include a novel palladium‐catalyzed asymmetric allylic alkylation reaction (Pd‐AAA) as well as a rhodium‐catalyzed chemo‐, regio‐, and stereoselective aziridination reaction.     

Mild and efficient Lewis acid-promoted detritylation in the synthesis of N-hydroxy amides: a concise synthesis of (-)-Cobactin T

An efficient, high-yielding Lewis acid promoted deprotection of O-trityl hydroxylamine derivatives is described. A range of acid-labile protecting groups, such as N-Boc and O-TBS, were tolerated under these mild conditions. The present method is applicable to the synthesis of a broad range of hydroxylamine derivatives, including N-hydroxy amides (hydroxamic acids), N-hydroxy sulfonamides, and N-hydroxy ureas, which often exhibit significant biological activities. An application of this methodology for a concise synthesis of (-)-Cobactin T (18) is also demonstrated.     

A concise synthesis of (R)- and (S)-α-alkyl isoserines from d- and l-malic acids

A simple and diastereoselective method for the synthesis of (R)- and (S)-α-alkyl isoserines has been developed in four steps starting from commercially available d- and l-malic acid, respectively. This approach features stereocontrolled alkylation of 2-(2-tert-butyl-5-oxo-1,3-dioxolan-4-yl)acetic acid and proceeds through a methylcarbamate via a Curtius rearrangement.     

Enantioselective synthesis of 2-arylpiperidines from chiral lactams. A concise synthesis of (-)-anabasine

Cyclodehydration of achiral or racemic aryl-delta-oxoacids with (R)-phenylglycinol stereoselectively affords chiral non-racemic bicyclic lactams, from which the enantiodivergent synthesis of (R)- and (S)-2-phenylpiperidine, the diastereodivergent synthesis of cis- and trans-3-ethyl-2-phenylpiperidine, and the enantioselective synthesis of the piperidine alkaloid (-)-anabasine is reported.     

A short and efficient synthesis of (R)-(−)-sporochnol A

A short and efficient synthesis of (R)-(−)-sporochnol A in five steps and 9% overall yield has been developed. The sequence uses as starting material the easily available enantiopure monoketal derived from 1,4-cyclohexanedione and (R,R)-hydrobenzoin that serves as a chiral auxiliary.     

Silver-promoted Friedel-Crafts reaction: concise total synthesis of (-)-ardeemin, (-)-acetylardeemin and (-)-formylardeemin

Total syntheses of multidrug resistant inhibitors (-)-acetylardeemin 2a, (-)-ardeemin 2b, and (-)-formylardeemin 3 have been achieved within 10 steps starting from bromopyrroloinoline 13. The key step involves direct alkylation of 13 with prenyl tributylstannane 11 to yield 12 via a silver-promoted asymmetric Friedel-Crafts reaction. Highly efficient installation of the isoprenyl group allowed excellent overall yield. Moreover, the substrate scope of the asymmetric Friedel-Crafts reaction of 13 was expanded to include a variety of arenes 14 to afford natural product-like library analogues 15.