Total synthesis of(-)-goniopypyrone

Recently,three novel styryl-lactones,goniofufurone,goniopypyrone,and 8-acetylgo-niotriol,which are cytotoxic to human tumor cells,have been isolated from the stembark of Goniothalamus species.Amongst these lactones,goniopypyrone is the mostbioactive.Its unusual natural skeleton was revealed by X-rav structure analysis to be     

Structural Studies of 3-(1,2-O-Isopropylidene-α-D-xylosyl)-5-phenyl-1,2,4-oxadiazole

Ourstudieswithlsonucleos！desandlsocarbonuc！eosldehavebeencarriedouttosearchforafltl．C3flCCF3fldfifltlV！rsl3CtlV！tICS‘2‘且SOCdfboflUCICOSldCIs3flCWCldSSO贯nUCICOSldCanalogueSInWhiChthefluCleobaSCIsllnkCdtothepOSitionOInbOSeOillerthanCIbycarbon－carbonbond．巨hesynthesisofcarbonucleosldeshasbeencaYFledoutsuccessfullyforseveralyears‘5’．Thesynthesisofderlvatlvesoff．2,4－oxadlazolecarbonucleosldebearingp－D－xylopyranosylmoietyhasbeenreported’·’．Someofthemshowe…     

Synthesis of Triphenyltin 2-(1,2-Ethylenedithio) Methylene-3-Oxo-5-Aryl-4-Pentenoate

ac-oxo-ketenedithioacetalsandrelatedcompoundsareversatileSynhlonsinorghocsynthesis.'"Althoughtherehavebeennumerousreportsaboutmisfieldinrecentyears,l-6allofthestUdiescanberoughlydividedintotwoaspectsfoneistheapplicahonofac-oxo-ketenedithioacetalsinorganicsyntilesis,andtileoilleristilesindiesontilereachvityadjustCdbythedialkylthiogroupsinac-oxo-betenedi1illoacetals.WehavedevotCdoureffortstothelatter."82-(l,2-ethylenedithio)medlylene-3-oxo-5-aryl-4-pentenoacids3wereformedbycondonsahonofacylketC…     

A Convenient One-Step Synthesis of 5-(α-alkanonyl) and 5-(α-Cyclanonyl)-4-Pentanolides

The thermolysis of t-butyl perpent-4-enoate in ketones leads to the formation of 5-(α-alkanonyl) and 5-(α-cyclanonyl)-4-pentanolides with fairly good yields.     

Total Synthesis of (-)-α-Pinguisene

In previous work from our laboratory, we demonstrated that α-carbonyl radical cyclization reactions can serve efficiently as key steps in total synthesis of natural products.1 In this presentation,we report the total synthesis of (-)-α-pinguisene from enone 1 via α-carbonyl radical cyclization.     

Synthesis of the 1,2-Dihydro 1,2-Δ3−azaphosphorines

Abstract

1,2-Dihydro 1,2-Δ³? azaphosphorines were prepared by reaction of dichlorophenylphosphine with two equivalents of imines. 2-Oxo 1,2-azaphospholenes were also obtained in some cases.     

A Synthesis of novel IH-Imidazo[1,2-α]Indole-3-Carboxylates

A route to the uncommon imidazo[1,2-α]indole nucleus 1 is described via functionalisation and annelation of readily accessible 2-amino-indole-3-carboxylates 5. Intramolecular cyclization of a key 2-indolylformamidate 6 was utilised for the preparation of the 3,9-diester intermediates 7.     

Synthesis of ( )-5α-Hydroxy-β-selinene and (-)-5β-Hydroxy-β-selinene

Eudesmanederivativeshavebeendrawingconsiderableattentionduetotheirwidespectrumofbiologicalproperties,particularlyantifeedant,cellgroWthinhibitoryandplantgroWthregulatingactivitiesl'2.Recently,twoepimericeudesmanederivatives( )-5a-hydroxy-6-selinene1and(-)-56-hydroxy-6-selinene2wereisolated3fromtheaerialpartsofCSubtraPicaFMell.,andtheirstructuresweredeterminedbyspectroscopicmethods.Herein,wereportafacilesynthesisofbothtwodiastereomers1and2from( )-dihydrocarvone3infivesteps,usingtheregioselect…     

A Total Synthesis of (±)-α-Chamigrene-3-one

Thephotocycloadditionofmethyl2,4-dioxopentanoate1toalkenesorconjugatedolefins2regioselectivelygavethecycloadduct3(Schemel).ThisreactioncouldconvenientlybeusedtoconstructthebasicframeworkofvariousnatUraIlyoccutringchamigran-tyPespirosesquiterPenes,suchasa-chamigrene",6-chamigrene:=,andaseriesofrelatedhaIogenatedderivativesd.The(i)-Q-Chamigrene-3-onewasanewmemberofthisfamilyandwasrecentlyisolatedfromMarchantiapolymorPha".whichpossessedthestrUctUreofasyntheticintermediate,1-methoxycarbonyl-5,…     

Batch emulsion copolymerization of 3‐O‐methacryloyl‐1,2:5,6‐di‐O‐isopropylidene‐α‐D‐glucofuranose and butyl acrylate: Synthesis and properties of the sugar latices

To obtain new polymer latices based on sugar derivative, batch emulsion copolymerizations of 3‐O‐methacryloyl‐1,2:5,6‐di‐O‐isopropylidene‐α‐D ‐glucofuranose (3‐MDG) and n‐butyl acrylate (BA) were carried out at 70 °C, with potassium persulfate as the initiator. 3‐MDG polymerizes faster than BA because of its higher reactivity ratio, r_(3‐MDG) = 1.94 versus r_(BA) = 0.54. The effect of the initial monomer composition on the polymerization rate and the thermal properties of the end copolymers was investigated. The overall rate of polymerization increases by enhancing the sugar content in the initial monomer composition. The glass‐transition temperature is linearly related to the sugar content in the copolymer. The influence of the type of surfactant showed that the particle size increases by changing from ionic to nonionic surfactant. Furthermore, the effect of the added acrylic acid (AA) on the rheological properties suggests that the sugar latices exhibit different non‐Newtonian flows depending on the pH of the latex and on the AA concentration on the particle surface. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 788–803, 2003     

2,3:4,6‐Di‐O‐isopropylidene‐α‐l‐sorbofuranose and 2,3‐O‐isopropylidene‐α‐l‐sorbofuranose

In the title compounds, C₁₂H₂₀O₆, (I), and C₉H₁₆O₆, (II), the five‐membered furanose ring adopts a ⁴T₃ conformation and the five‐membered 1,3‐dioxolane ring adopts an E₃ conformation. The six‐membered 1,3‐dioxane ring in (I) adopts an almost ideal ^OC₃ conformation. The hydrogen‐bonding patterns for these compounds differ substantially: (I) features just one intramolecular O—H...O hydrogen bond [O...O = 2.933 (3) Å], whereas (II) exhibits, apart from the corresponding intramolecular O—H...O hydrogen bond [O...O = 2.7638 (13) Å], two intermolecular bonds of this type [O...O = 2.7708 (13) and 2.7730 (12) Å]. This study illustrates both the similarity between the conformations of furanose, 1,3‐dioxolane and 1,3‐dioxane rings in analogous isopropylidene‐substituted carbohydrate structures and the only negligible influence of the presence of a 1,3‐dioxane ring on the conformations of furanose and 1,3‐dioxolane rings. In addition, in comparison with reported analogs, replacement of the –CH₂OH group at the C1‐furanose position by another group can considerably affect the conformation of the 1,3‐dioxolane ring.     

Methyl 4‐O‐β‐D‐mannopyranosyl β‐D‐xylopyranoside

Methyl β‐D‐mannopyranosyl‐(1→4)‐β‐D‐xylopyranoside, C₁₂H₂₂O₁₀, (I), crystallizes as colorless needles from water, with two crystallographically independent molecules, (IA) and (IB), comprising the asymmetric unit. The internal glycosidic linkage conformation in molecule (IA) is characterized by a ϕ′ torsion angle (O5′_Man—C1′_Man—O1′_Man—C4_Xyl; Man is mannose and Xyl is xylose) of −88.38 (17)° and a ψ′ torsion angle (C1′_Man—O1′_Man—C4_Xyl—C5_Xyl) of −149.22 (15)°, whereas the corresponding torsion angles in molecule (IB) are −89.82 (17) and −159.98 (14)°, respectively. Ring atom numbering conforms to the convention in which C1 denotes the anomeric C atom, and C5 and C6 denote the hydroxymethyl (–CH₂OH) C atom in the β‐Xylp and β‐Manp residues, respectively. By comparison, the internal glycosidic linkage in the major disorder component of the structurally related disaccharide, methyl β‐D‐galactopyranosyl‐(1→4)‐β‐D‐xylopyranoside), (II) [Zhang, Oliver & Serriani (2012). Acta Cryst. C 68 , o7–o11], is characterized by ϕ′ = −85.7 (6)° and ψ′ = −141.6 (8)°. Inter‐residue hydrogen bonding is observed between atoms O3_Xyl and O5′_Man in both (IA) and (IB) [O3_Xyl...O5′_Man internuclear distances = 2.7268 (16) and 2.6920 (17) Å, respectively], analogous to the inter‐residue hydrogen bond detected between atoms O3_Xyl and O5′_Gal in (II). Exocyclic hydroxymethyl group conformation in the β‐Manp residue of (IA) is gauche–gauche, whereas that in the β‐Manp residue of (IB) is gauche–trans.     

Synthesis of benzyl O-(2,3,3'-tri-O-acetyl-β-D-apiofuranosyl)-(1→3)-2,4-di-O-benzoyl-α-D-xylopyranoside and its X-ray structure

The protected apiose-containing disaccharide, benzyl O-(2,3, 3'-tri-O-acetyl-β-D-apiofuranosyl)-( 1→3)-2, 4-di-O-benzoyl-α-D-xylopyranoside, was synthesized and its X-ray structure provided.     

Convenient synthesis of poly(γ‐benzyl‐L‐glutamate) from activated urethane derivatives of γ‐benzyl‐L‐glutamate

A series of activated urethane‐type derivatives of γ‐benzyl‐L ‐glutamate were synthesized, and their potential as monomers for polypeptide synthesis was investigated. The derivatives of the focus of this work were a series of N‐aryloxycarbonyl‐γ‐benzyl‐L ‐glutamate 1 , of which aryl groups were phenyl, 4‐chlorophenyl, and 4‐nitrophenyl. These urethanes 1 were reactive in polar solvents such as dimethylsulfoxide, N,N‐dimethylformamide (DMF), and N,N‐dimethylacetamide (DMAc), and were efficiently converted into poly(γ‐benzyl‐L ‐glutamate) (poly(BLG)) under mild conditions; at 60 °C without addition of any catalyst. Among the three urethanes, that having 4‐nitrophenoxycarbonyl group 1c was the most reactive to give poly(BLG) efficiently, as was expected from the highly electron deficient nature of the nitrophenoxycarbonyl group. On the other hand, the urethane 1a having phenoxycarbonyl group was also efficiently converted into poly(BLG), in spite of the intrinsically less electrophilicity of the phenoxycarbonyl group. In addition, the successful formation of poly(BLG) by the reaction of 1a favored its diluted concentration (0.1 M) much more than 2.0 M, the optimum initial concentration for 1c . ¹H NMR spectroscopic analyses of the reactions in situ revealed that the predominant pathway from 1 to poly(BLG) involved the intramolecular cyclization of 1 into the corresponding N‐carboxyanhydride, with release of phenol and its successive ring‐opening polymerization with release of carbon dioxide. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2649–2657, 2008