Stereoselective Synthesis of α-L-Rhamnopyranosyl Phosphonates via α-L-Rhamnopyranosyl Trifluoroacetate

α-L-Rhamnopyranosyl phosphates 8a-b～12a-b were obtained in high yield and high stereoselectivity from α-L-rhamnopyranosyl trifluoroacetate 2a-b and phosphoric acid diesters in the presence of a Lewis acid.     

Formal Synthesis of (+)-α-Conhydrine and Stereoselective Synthesis of Pyrrolidine Analogue via the Diastereoselective Chelation-Controlled Hydride Reduction and Wittig Reaction

Asymmetric syntheses of (+)-α-conhydrine and its pyrrolidine analogue were achieved from readily available L-serine. The key step involved highly diastereoselective chelation-controlled hydride reduction of the amino ketone to give the anti-amino alcohol and Wittig reaction.     

A Facile Stereoselective Synthesis of Ether-Linked β-D-Maltosyl- and β-D-Lactosyl-glycerolipids via Peracetylated Disaccharide α-Phosphoramidates

The reaction of 1-O-hexadecyl-2-O-methyl-sn-glycerol with 2,3,6,2′,3′,4′,6′-hepta-O-acetyl-α-lactosylphosphoramidate or α-maltosylphos-phoramidate in the presence of trimethylsilyl triflate and molecular sieves afforded 1-O-hexadecyl-2-O-methyl-3-O-(2,3,6,2′,3′,4′,6′-hepta-O-acetyl-β-lactosyl)-sn-glycerolipid or β-maltosyl-sn-glycerolipid stereoselectively in moderate yields after column chromatography. Alkaline hydrolysis of the O-peracetyl glycerolipids gave the desired β-glycolipids 1 and 2.     

Stereoselective Synthesis of (E) or (Z) α-Alkenylphosphonates via α-Stannylated Phosphonates

α-lithiostannylalkylphosphonates react with aldehydes with the complete elimination of the organotin moiety. The stereoselective formation of the (E) or (Z) α-alkenylphosphonates is closely dependent on the tin substituent.     

Stereoselective Synthesis of α-Aminonitril on Glucose Templates

Both proteinogenic and non proteinogenic α-amino acids are of particular interest as constituents of peptide factors, peptidomimetics and antibiotics for the construction of modern selective drugs. [1] Furthemore, α-amino acid derivatives are interesting building units for chiral-pool syntheses of enantiomerically pure natural products. [2] Numerous efforts in modern organic synthesis are centered on the synthesis of enantiomerically pure α-amino acids. [3] During the past three decades efficient methods of asymmetric synthesis of α-amino acids have been developed; most of them are based on electrophilic transformations of organometallic intermediates. [4] Using the concept that the chirality of the carbohydrates can be exploited for diastereoselective reactions, Kunz and his cooperator had developed a Strecker synthesis with glycosyl amines as chiral auxiliaries. [5]     

Stereoselective Synthesis via Chiral Pinanone Imine

A serious of new pinanone ketimine, and of which asymmetric alkylation, carbonyl additionand double chiral induction reaction have been studied. The ketimine with π-structure are essential toobtain excellent stereoselectivities in 90%～99%e.e. They are explained by the transition model thatwe proposed.     

Stereoselective Synthesis of Novel C-Disaccharides via Suzuki Cross-Coupling Reaction

Novel β-C-disaccharides containing a three carbon linkage using exo-glycal as the precursor were prepared stereoselectively. The synthesis was achieved by the tandem reactions of the stereoselective hydroboration of exo-glycal and Suzuki cross-coupling reaction with an iodovinyl sugar, and followed by hydrogenated deprotection under the catalysis of Pd（OH）2/C.     

Stereoselective Synthesis of α-Methylene-β-Hydroxy-γ-Alkoxy Esters and Ketones

The amine catalysed aldol-type addition of vinylcarbonyl units to α-alkoxy aldehydes proceeds with reasonable diastereoface selectivity to afford the title compounds in good yield.     

C- and O-Alkylation with α-Haloketones of the Adamantane Series

Reactions of 1-adamantyl bromomethyl ketone and 1-(1-adamantyl)-3-bromo-2-propanone with acetylacetone and ethyl acetoacetate in a mixture of dry diethyl ether with anhydrous methanol in the presence of sodium methoxide afforded 3-(1-adamantylcarbonylmethyl)-2,4-pentanedione, ethyl 2-(1-adamantylcarbonylmethyl)-3-oxobutanoate, 4-acetyl-1-(1-adamantyl)-2,5-hexanedione, and ethyl 2-acetyl-5-(1-adamantyl)-4-oxopentanoate. The Knoevenagel-Cope reactions of 1-adamantyl bromomethyl ketone and 1-(1-adamantyl)-3-bromo-2-propanone with diethyl malonate yielded, respectively, diethyl 1-(1-adamantyl)-2-bromoethylidenemalonate and diethyl 1-(1-adamantylmethyl)-2-bromoethylidenemalonate. O-Alkylation of ethyl acetoacetate with 1-adamantyl bromomethyl ketone gave ethyl 3-(1-adamantylcarbonylmethoxy)-2-butenoate. Carboxylic acids reacted with 1-adamantyl bromomethyl ketone to form the corresponding 2-(1-adamantyl)-2-oxoethyl carboxylates.     

A Short and Highly Stereoselective Synthesis of Cerebrosterol

Ｃｅｒｅｂｒｏｓｔｅｒｏｌ (2 4Ｓ ｈｙｄｒｏｘｙｃｈｏｌｅｓｔｅｒｏｌ,1)ｆｏｒｍｅｄｉｎｓｍａｌｌａｍｏｕｎｔｓｉｎｈｕｍａｎａｎｄａｎｉｍａｌｂｒａｉｎ1ｆｒｏｍｃｈｏｌｅｓ ｔｅｒｏｌｉｓｉｍｐｏｒｔａｎｔｆｏｒｃｈｏｌｅｓｔｅｒｏｌｈｏｍｅｏｓｔａｓｉｓｉｎｔｈｉｓｏｒｇａｎ .Ｔｈｅｅｘｃｅｓｓｃｈｏｌｅｓｔｅｒｏｌｉｓｃｏｎｖｅｒｔｅｄｉｎｔｏ 2 4Ｓ ｈｙｄｒｏｘｙ ｃｈｏｌｅｓｔｅｒｏｌｂｙａｕｎｉｑｕｅｂｒａｉｎ ｓｐｅｃｉｆｉｃ 2 4Ｓ ｈｙｄｒｏｘｙｌａｓｅ ,ｗｈｉｃｈｃｏｕｌｄｂｅｒ…     

Stereoselective Synthesis and Bioactivities of New ω-Azolyalkenes

ManyN-vinyltriazolesareeffectivefungicides"',theyhavebeenf()undtoinhibitbiosynthesisofergosterolinfungalcells,suchasdiniconazo1e(S-33O8)anduniconazole(S-33O7).Owingtothemechanismofthebioactivitiesrelatescloselytoconfigurationofthisfungicidals,newsyntheticmethodsareneedednotonlythenovelcarbonskeletonbutalsogoodconditionsfOrgettingageometricalisomerwhichshowsbetterfungicidalactivity.Fromthispointofview,alsoourpreviousworkaboutylidechemistry',wedesignedaroutetothestereoseletivesysthesisofthetit…     

Stereoselective Synthesis of γ-hydroxy-α-amino acids via intramolecular amidomercuration

A general method for the stereoselective conversion of homoallylic alcohols to erythro- or threo-β-hydroxy-α-amino acids is described. The key step is the stereoselective mercuric ion-initiated cyclofunctionalization of acylaminomethyl ether derivatives of the homoallylic alcohols (3 → 8). The stereochemistry of the products obtained from the cyclofunctionalization is controlled by the choice of reaction conditions. Reaction under conditions of kinetic control leads to predominant formation of cis 4,6-disubstituted tetrahydro-1,3-oxazines, while reaction under conditions which allow for equilibration of the organomercurial intermediates results in the formation of the trans stereoisomer with very high stereoselectivity. Oxidative demercuration and oxidation of the resulting alcohol produces a protected form of the title amino acids (8 → 9 → 10). Cleavage of the tetrahydrooxazine ring with hydrobromic acid then produces the amino acid products asγ-butyrolactone hydrobromides (11 and 12). This general method thus allows for stereoselective synthesis of either diastereomer of the amino acid product starting with a single homoallylic alcohol.     

Stereoselective Synthesis of （R）-Salmeterol via Asymmetric Cyanohydrin Reaction

The authors described a short and highly enantioselective route to （R）-salmeterol involving asymmetric synthesis of cyanohydrin followed by nucleophilic substitution with 6-（4-phenylbutoxy） hexyl methanesulfonate.     

NaOH/Et3N-Promoted Stereoselective One-Pot Synthesis of α-Diazo Oxime Ethers via Diazo Transfer Reaction

For the first time, we have observed a combined effect of two bases NaOH/Et₃N to promote the diazo transfer reaction of β-oximino esters. This unusual synergistic effect has been employed to obtain α-diazo oxime ethers directly from β-keto esters by one-pot process. This method is simple and cost-effective and the reagents are readily available.     

Stereoselective Synthesis of Sulfonyl-substituted trans-2,3-Dihydrofuran Derivatives via Reaction of Arsonium Ylides with α,β-Unsaturated Ketones

Trans-2,3-dihydrofuran derivatives 3 or 4 substituted with a sulfonyl group were prepared with high chemoselectivity and good yields by [1＋4]-addition reaction of α,β-unsaturated ketones 1 with arsonium bromide 2 in CH2Cl2 in the presence of potassium carbonate at room temperature.The structures of the products were characterized by IR,MS,^1H NMR,elemental analysis and single crystal X-ray diffraction analysis.A mechanism for the formation of products was also proposed.     

Cobalt-Catalyzed Asymmetric Deuteration of α-Amidoacrylates for Stereoselective Synthesis of α,β-Dideuterated α-Amino Acids

A cobalt-catalyzed deuteration of amidoacrylates using deuterated methanol afforded α,β-dideuterio-α-amino esters in excellent enantiomeric ratios (mostly >95 : 5) and almost complete deuteration (99 %). The new protocol was used to prepare dideuterio-α-amino acid fragments in some drugs. Furthermore, the stereoselective deuteration was applied in a concise synthesis of dideuterio l -DOPA.     

Stereoselective Total Synthesis of Chrysanthemol

Recently,muchattentionhasbeenpaidtothesynthesisofbioactivenaturalproducts.Chrysanthemol,aneudesmanetypesesquiterpene,firstisolatedfromChrysanthemumindicumL.byD.Q.Yuetal.',showedstrongantiinflanunatoryactivityinmice.ThestructureandabsolutestereochemistryofchrVsanthemolwereelucidatedas1ThesyntheticrouteofchrysanthemolflomR-( )-carvoneisdepictedinScheme1:n.50%aqACOH,2hr;d)KOH,EtOH,oOC,3hr,e)Na,propanol,50"C,6hr,67.2%;66.7%i)m-CPBA/NaHCO3,CHZC12,r.t.,3.5hr,84%;TreatmentofR-( )-carvon…     

The Stereoselective Synthesis of Indoloquinolizines

Carboline was reduced with lithium aluminum hydride to provide carboline-alcohol whichreacted with methyl vinyl ketone to form the corresponding hydroxymethyl-amino-ketone. Underphase transfer condition it can be converted into enantiomerically pure indoloquinolizines. The cycliza-tion mechanism was also illustrated here.