Asymmetric Synthesis of (-)-(2R,3R,6S)-Irnigaine

Introduction　　Asarelativelynewmemberofnaturalalkaloidswith2 ,6 disubstituted 3 piperidinolskeleton ,irnigaine 1wasisolatedfromthetubersofArisarumVulgare (Araceae)in1995byMelhaouiandBode .1Itsstructureandrelativeconfigurationswereelucidatedby1HNMRstudiesandtheabsoluteconfigurationwasproposedonthebasisofitsopti calrotation .1Soonafterthen ,Meyerandhisco workersreportedthefirstsynthesisof (- ) (2R ,3R ,6S) irni gaineandtheconfigurationconfirmation .Althoughtheirsynthesisroutewasshortan…     

Stereoselective Synthesis of [Rp]-Dinucleoside (3′,5′)-Methanephosphonates

Abstract

DBU-assisted phosphonylating properties of diastereomerically pure 5′-O-DMT- thymidine (O-2,4,6-trimetylbenzoyl methanephosphonothiate)(1) towards alcohols [1] have been used for the synthesis of [Rp]-dithymidylyl(3′,5′)-methanephosphonothiótes (2) and metanephosphonates (3). Substrates (4) and (5) have been obtained according to the previously described methods [2].     

Synthesis of Quinolone Analogues： 7-[（2S, 4R）-2-Aminomethyl-4- hydroxypyrrolidin-l-yl] Quinolones

New quinolone derivatives of 7-[(2S, 4R)-2-aminomethyl-4-hydroxypyrrolidin-l-yl] quinolone-3-carboxylic acids were synthesized by condensation of 7-halo substituted quinolone-3-carboxylic acids with (2S, 4R)-2-aminomethyl-4-hydroxypyrrolidine. These compounds were characterized by FAB-MS and IH NMR.     

Synthesis of stereospecifically labeled carbohydrates: Preparation of (3S)− and (3R)-[3-2H1]ascarylose

The general problem of the synthesis of 3,6-dideoxy sugars containing stereospecifically labeled hydrogen isotope at C-3 is addressed for the specific case of ascarylose (3,6-dideoxy-L-arabino-hexose).     

Synthesis of spiro[bicyclo[2.2.1]heptane-2,2′-furan]-3-amines via stereoselective cycloadditions of trimethylenemethane to (1S,3EZ,4R)-3-arylimino-1,7,7-trimethylbicyclo[2.2.1]heptan-2-ones

Stereoselective [3+2] cycloadditions of trimethylenemethane (TMM) to the exocyclic CO and CN double bonds of (1S,3EZ,4R)-3-arylimino-1,7,7-trimethylbicyclo[2.2.1]heptan-2-ones gave the corresponding spiro[bicyclo[2.2.1]heptane-2,2′-furan] and spiro[bicyclo[2.2.1]heptane-3,2′-pyrrolidine] derivatives. Further stereoselective reductions of the CN or CO bond in these cycloadducts furnished new chiral amines, diamines, and a new aminoalcohol. All cycloadditions and reductions of the CN double bonds took place from the less hindered endo-face of the (1S,3EZ,4R)-3-arylimino-1,7,7-trimethylbicyclo[2.2.1]heptan-2-ones, exclusively, thus giving the corresponding products in 100% de. The structures were determined by NMR, NOESY spectroscopy, and by X-ray diffraction.     

Stereoselective Synthesis of [3.3.0]‐Fused γ‐Butyrolactones of Carbohydrates

A facile and stereoselective method is described for the preparation of fused 2,3‐γ‐butyrolactones of lyxofuranose from the unexpected rearrangement in basic media of the photocycloadduct between homochiral 2(5H)‐furanones and vinylene carbonate.     

Synthesis of 4-Hydroxy 6-Methyl 3-β-Arylpropionyl 2-Pyrones by Selective Catalytic Hydrogenation of 3-Cinnamoyl 4-Hydroxy 6-Methyl 2-Pyrones

We report a simple method for synthesis of 4-hydroxy 6-methyl 3-β-arylpropionyl 2-pyrones 1 from 3-cinnamoyl 4-hydroxy 6-methyl 2-pyrones by selective hydrogenation at ambient temperature under pressure using 10% palladium on carbon as catalyst.     

Study on the Stereoselective Synthesis of Carbapenem Sidechain （2S,4S）-4-Acetylsulphanyl-2- [（S）-l-phenylethylcarbamoyl]- pyrrolidine-l-carboxylic Acid 4-Nitrobenzyl Ester

A stereoselective and economic synthesis of the carbapenem sidechain (2S, 4S)-4-ace-tylsulphanyl-2- [ (S) 1-phenylethyl-carbamoyl] pyrrolidine-l-carboxylic acid 4-nitrobenzyl ester was developed. Due to the effect of spatial hindrance, only the (2S,4S) diastereomer 3 was obtained by coupling 1 and the inexpensive racemic 2 catalyzed by EEDQ.     

Stereoselective synthesis of 2-substituted 3-azabicyclo[3.2.0]heptan-2-ones by [2+2]-cycloaddition of N-allyl-β-N-keteniminium salts derived from (R)-vinylglycinol

A stereoselective synthesis of (1R,2R,5S)-2-benzyloxymethyl-3-azabicyclo[3.2.0]heptan-2-one was achieved, by intramolecular [2+2]-cycloaddition of (R)-vinylglycinol-derived N-allyl-β-N-keteniminium salts, with high facial diastereoselection. The regio- and stereochemical courses have been qualitatively investigated by Molecular Mechanics calculations.     

Stereoselective Synthesis of syn-and anti-3a-Hydroxyl-1,2,3,3a,8,8a-hexahydropyrrolo[2,3-b] indole-2-carboxylic Acid

The structure of syn-and anti-N^b-(p-toluenesulfonyl)-3a-hydroxyl-1,2,3,3a,8,8a-hexahydro pyrrolo[2,3,-b]indole-2-carboxylic t-butyl ester was stercoselectively synthesized by oxidative ring formation of N^b-(p-toluenesulfonyl)-L-tryptophan t-butyl ester in methylene chloride containing dimethyldioxirane(DMDO),the p-toluenesulfonly group and t-butyl group can be easily removed by sodium naphthalenide and trifluoroacetic acid,respectively.     

Stereoselective Synthesis of Tricyclo[6.2.2.02,7]dodecane-3,6,9,10-tetrol via Selective Reduction of α,β-Unsaturated 1,4-DIKetone

Stereoselective synthesis of tricyclo[6.2.2.0^2,7]dodecane-3,6,9,10-tetrol was developed starting from p-benzoquinone. The endo selective Diels–Alder cycloaddition of p-benzoquinone and 1,3-cyclohexadiene afforded the corresponding bicyclic diketone. The synthesis of the title compound was based on the cycloadduct by selective reduction with NaBH₄, acetylation with AcCl, and hydroxylation with OsO₄-NMO.

[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource: Full experimental and spectral details.]     

Synthesis and structural characterization of camphanates of (−)-(2S3S,3S) and (+)-(2S,3R)-4-Phenyl-3-bromo-2-butanol diastereoisomers

The X-ray crystal structures of (–)-syn-4-phenyl-3-bromo-2-butyl camphanate (I) and (+-anti-4-phenyl-3-bromo-2-butyl camphanate (II) have been determined. Thesyn diastereoisomer of bromohydrin has the (2S,3S) absolute configuration whereas theanti diastereoisomer has the (2S,3R) absolute configuration. The crystallized derivatives I and II have been obtained by the reaction of each stereoisomer of bromohydrin, synthesized by reduction with baker's yeast, with (1S)-camphanic chloride. Crystal data: (I) C₂₀H₂₅BrO₄:M _w: 409.32; orthorhombic,P2₁2₁2₁;a=11.245(3),b=12.086(1),c=14.512(4) å; Z=4; finalR=0.053 for 1819 observed reflections. (II) C₂₀H₂₅BrO₄;M _w=409.32; monoclinic, P2₁;a=11.352(1),b=6.378(1),c=14.255(2) å,=110.38(1);Z=2; finalR=0.045 for 1672 observed reflections.     

Asymmetric synthesis of heteroorganic analogs of natural products 5. Synthesis of pure diastereomers and enantiomers of fluoro-substituted (2S,3R)- and (2R,3R)-β-phenylserines

A convenient method is proposed for the preparative synthesis of pure diastereomers and enantiomers of fluoro-substituted (2S,3R)- and (2R,3R)--phenylserines by the hydroxyalkylation of the Ni(II) — complex of the Schiff base of glycine with (S)-2-N-(N¹-benzylpropyl)aminobenzophenone using the corresponding fluoro-substituted benzaldehydes.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya. No. 8, pp. 1906–1913, August, 1991.     

Phase Transfer Catalyzed Synthesis of 1, 2-Bis[（3-aryl）-s-triazolo- [3, 4-b]-[1, 3, 4]thiadiazole-6-yl]ethanes

s-Triazolo[3, 4-b]-[1, 3, 4]thiadiazole derivatives have been paid attractive attention due to their significantly biological activities1-5, including antibacterial, antifungal, anticancer, relaxing vascular activities. They are highly important heterocyc…     

Stereoselective Synthesis of (Z)-β-Aryltellurocinnamic Esters

ＳｔｅｒｅｏｓｅｌｅｃｔｉｖｅＳｙｎｔｈｅｓｉｓｏｆ（Ｚ）－β－ＡｒｙｌｔｅｌｌｕｒｏｃｉｎｎａｍｉｃＥｓｔｅｒｓ￥ＣｈａｎｇＱｉｕＺＨＡＯ；ＸｉａｎＨＵＡＮＧ（ＤｅｐａｒｔｍｅｎｔｏｆＣｈｅｍｉｓｔｒｙ，ＨａｎｇｚｈｏｕＵｎｉｖｅｒｓｉｔｙ，Ｈａｎ...     

Synthesis of 1-[6-Fluoro-(2S)-3H,4H-dihydro-2H-2-chromenyl]-(1R)-1,2- ethanediol and 1-[6-Fluoro-(2R)-3H,4H-dihydro-2H-2-chromenyl]- (1R)-1,2-ethanediol

Benzopyran compounds possess diverse pharmacological properties such as β-blockade, anticonvulsant and antimicrobial.[1,2] Our interest has been focused on the synthesis of 1-[6-Fluoro-2S]-3H,4H-dihydro-2H-2-chromenyl]-(1R)-1,2-ethanediol (6) and 1-[6-fluoro-(2R)-3H,4H-dihydro-2H-2-chromenyl]-(1R)-1,2-ethanediol (7) which are particularly convenient precursor to (S,R,R,R)-NE (8). 8 containing four asymmetrical carbon atoms was reported to be the most active isomer.[3] Chandrasekhar[4] has reported on the synthesis of 8. The key step to synthesize this compound is to obtain the chiral chromanone 6 and 7. 6 was accomplished in 8 steps by the Clasien rearrangement and a one-pot Sharpless asymmetric epoxidation, but the compound 7 was accomplished in 10 steps. Johannes[5] used Zr-catalytic kinetic resolution of allylic ethers and Mo-catalyzed chromene formation to synthesize 8 in 14 steps. However both of the methods request many synthetic steps and expensive reagents.     

Synthesis and structural studies of (1R,2R,5R)-chloro{o-[β-(2-hydroxy-2,6,6-trimethylbicyclo[3.1.1]hept-3-ylidenamino)ethyliminomethyl]phenoxy-O,N,N}palladium(II)

The reaction of (1R,2R,5R)-3-[{2-[(2-hydroxybenzylidene)amino]ethyl}imino]-2,6,6-trimethylbicyclo[3.1.1]heptan-2-ol with lithium tetrachloropalladate was studied. A chiral palladium(II) complex was thus obtained and its structure was confirmed by NMR spectroscopy and X-ray diffraction analysis.     

Stereoselective Synthesis of cis-1, 2-cyclopropane Derivatives

IntroductionNumeroussyntheticmethodsofcyclopropanationhavebeenstudied[l1,butmostofthemarenon-stereoselective,oritsproductisthethermodynamicallystableonewithl,2-transconfiguration.Thestereoselectivesynthesesof1,2-cisisomersofcyclopropanederivativesareseldomseeninliterature.Hereinastere-oselectivecycloporpanationviathereactionofarsenicylidewithe1ectrondefi-cientalkenesisreportedinthispaper.ResultsandDiscussionCarbomethoxymethylenetriphenylarl,oritsarsoniumbromideinthepresenceofK,CO,reactswith2…