Methyl-2,6-Anhydro-α-D-Mannofurahosid Eine Verbesserte Darstellungsmethode Sowie Die Bestimmung Der Kristall- Und Molekolstruktur

Abstract

The title compound 3, which is the first member of a new class of anhydroglycosides, was initially isolated from the methanolysis mixture of the pyranoid isomer 1 in about 1% yield. Improved yields of greater than 30 % of 3 are obtained by treating the main product of the aforementioned methanolysis, the dimethylacetal 2, with a catalytic amount of p-toluenesulfonic acid in boiling xylene. 3 (C₇H₁₂O₅) crystallizes from diisopropyl ether in the monoclinic space group P21 (Z=2) with a = 552.4(1), b = 685.2(1), c = 1052.9(3) pm, α = 90.0, β = 98.95(6) and Y = 90.0°. The structure was solved by X-ray crystal structure analysis using direct methods to R indices of 0.036 and 0.045, respectively, for 1180 independent reflections. The furanoid ring in 3 adopts a conformation intermediate between ²T₃(D) and E₃(D) (puckering parameters: Q = 48.9 pm; Φ = 102.4°). The oxane ring adopts an ^a2C_a5(D) conformation, which is heavily distorted by flattening at C-6 (puckering parameters: Q = 64.2 pm; Φ = 58.1° and 0 = 159.5°). Orientation of the glycosidic methyl group is in accord with the exo-anomeric effect. The molecules of 3 are interchained in three dimensions by a system of hydrogen bonds.     

Free Radical Ring-Opening Polymerization of 4-n-Hexyl- and 4-n-Decyl-2-methylene-1,3-dioxolanes

Two alkyl-substituted cyclic ketene acetals, 4-n-hexyl-2-methylene-1,3-dioxolane (4) and 4-n-decyl-2-methylene-1,3-dioxolane (6), were shown to undergo free radical ring-opening polymerization with the introduction of an ester group into the backbone of an addition polymer. The spontaneous polymerization of 4 (presumable by an ionic mechanism) produced a polymer containing no ring-opened units; furthermore 4 and 6 could be stabilized with respect to spontaneous polymerization by the addition of small amounts of pyridine. On the other hand, the polymerization of 4 in a 50% (by weight) benzene solution at 110°C with di-tertbutyl peroxide as the catalyst gave quantitative ring opening to give a polyester containing both possible isomeric ring-opened units. Bulk polymerization of 4 at 60°C at 53% conversion gave 50% ring opening which was divided 31% to 19% between cleavage to give the intermediate secondary free radical and the intermediate primary radical. Copolymerization of 4 with equimolar quantities of styrene at 110°C gave at 56% conversion a copolymer consisting of 67% styrene units, 22% ester-containing units resulting from cleavage to form a secondary radical, 7% of the isomeric ester-containing units, and 4% nonring-opened units. Polymerization studies with monomer 6 gave results very similar to those obtained with 4.     

The structure of cis and trans lsomers of 1-(p-Bromobenzylidene)-2-indanone

Abstract

In this communication we wish to report an interesting case of the isolation and characterization of the cis and trans isomers of 1-(p-bromobenzylidene)-2-indanone and their ketals. Prior to this work, Hoogstreen and Trenner² had reported on the cis and trans isomers of 1-(p-chlorobenzylidene)-2-methyl-5-methoxyindenylacetic acid. The condensation of 2-(N-morpholinyl)-indene (1, prepared by the reaction of 2-indanone³ and morpholine) with P-bromobenzaldehyde was conducted by refluxing them in the presence of acetic acid for 4 hours. Acid hydrolysis of the reaction mixture followed by dry column chrcmatography over sillica gel using a fraction collector afforded two iscmeric monobenzylidenes, compounds 2(36.6%, mp 110–111°)and 3(1.3%, mp 115–116°) and a dibenylidene, compound 4 (8.7%, mp 205°). The relative rations of the mono- and dibenzylidenes seemed to depend on the reaction conditions. Higher yields of the monobenzylidenes 2 and 3 were obtained by conducting the reaction in the presence of UV light. The structures of these monobenzylidenes were established as cis and trans isomers of 1-(p-bromobenzylidenes)-2-indanone on the Basis of elemental analyses and ir and nmr spectroscopy. The ir spectra⁴ (CHCl₃)

of compounds 2 [1725 (c=0), 1620 (c=c)cm^?1] and 3[1710 (c=o), 1570, 1600 (c=c) cm^?1] were consistent with the structures. The molecular ion peaks as well as the fragmentation patterns in the mass spectra of both these compounds were consistent with the assigned structures. Before going into the omr discussion it should be pointed out that treatment of compound 2 with athylene glycol in the presence of p-toluene sulfonic acid produced two ketals, 5 (38.3% mp, 118–120°) and 6 (30.6% mp, 125–126°). As depicted; the ketals 5and 6 were also found (by omr) to be related to each other as cis and trans isomers. Furthermore, each of them could be hydrolyzed with acid to the corresponding monobenzylidenes 2 and 3 without any isomerization. However, UV irradiation of compounds 2 and 3 gave equilibrium mixtures containing both the isomers, indicating isomerization had occurred under photolytic conditions.     

Occurrence of the Unusual 2C5 (1C4) Chair Conformation in Two Carbohydrates and the Reverse Anomeric Effect. X-Ray Structures of 3,4,5,7-Tetra-O-Acetyl-2,6-Anhydro-D-Glycero-D-Ido-Heptonamide (1) and 3,4,5,7-Tetra-O-Acetyl-2,6-Anhydro-D-Glycero-L-Gluco-Heptonamide (2)

Abstract

The title compounds 1 and 2 (both C₁₅O₁₅NH₂₁) crystallized in the monoclinic space group P2₁ (Z = 2) with a=8.864(1), b=8.346(1), c =13.569(1)Å, β =114.12(1), V=918.1(2)A3, D(calc) = 1.358 g/cc for compound 1, and a=15–045(1), b=8.106(1), c=7.491(1)Å, β =97.23(1)°, V=906.4(3)Å3 D(calc)= 1.375 g/cc, for compound 2. The structures were solved by direct methods and refined by the full-matrix least squares technique to R indices of 0.010 and 0.046, respectively. Both compounds are in the α ? D configuration and adopt the unusual ²C₅, (¹C₄) chair conformation with the carbamoyl groups on the anomeric carbon atoms equatorially oriented. In this conformation the orientations of the substituents are 2e, 3a, 4a, 5a and 6a in 1 and 2e, 3a, 4a, 5e and 6a in 2 which leads to unfavorable 1,3-diaxial interactions. The “reverse anomeric effect” which induces the ²c₅ chair conformation in these compounds, may have its origin in the unfavorable steric interactions found in the ⁵c₂ (⁴C₁) conformation where the carbamoyl group is axially oriented. Furthermore, the ²C₅ conformation is stabilized by the N-H … O intramolecular hydrogen bond between the carbamoyl nitrogen atom and the pyranosyl ring oxygen atom. Semi-empirical energy calculations reveal that the rotational freedom of the carbamoyl group is greater for the equatorial orientation (²C₅) than for the axial orientation (⁵C₂).     

New Approach Towards Carotane Sesquiterpenes: A Short Synthesis of (−)-Daucene

Abstract

An enantioselective synthesis of sesqui-terpene hydrocarbon (?)-daucene 1 from R-(+)-limonene involving acid catalysed enone- olefln cyclisation (5° 6) as the key step is described.     

Crystalline Methyl β-L-Pfamnofuranqside From Fischer Glycqsidatiok of L-Rhamnose

Flash chromatography of the mixture obtained by reaction of L-rhamnose with methanol in the presence of cation-exchange resin, in addition to methyl α-L-rhamnofuranoside (3) and methyl rhamnopyranosides 1 and 2 gave methyl β-L-rhamnofuranoside (4) in 8% yield. ¹³C and ¹H NMR spectra of 3 and 4 as well as their calculated conformation in solution are discussed.     

New Homologation Procedures of Carbonyl Compounds by Means of Diethyl[trimethylsilylethoxymethyl]phosphonate

Abstract

The lithiated carbanion of the phosphonate 1 prepared by means of s-BuLi at -78°C in THF can be treated with C1Si(CH₃)₃ transforming 1 into its α-Si(CH₃₎₃ substituted derivative 2. Whereas the anion of 1 is thermally unstable at temperatures exceeding -70°C the preparation of the corresponding carbanion of 2 by means of s-BuLi and the subsequent reaction with carbonyl compounds can be carried out at temperatures about -30°C illustrating the carbanion stabilizing effect of the α - silyl group. The phosphonate 2 is very suitable to effect conversion of many aldehydes and ketones via the vinylphosphonate-type 3 (applying a Peterson elimination) either to the homolocles esters 4 or the special α -hydroxyesters 5.     

Synthesis and X-Ray Crystal Structure of Methyl D,L-Desmeihyl-Holantosaminide

4-Acetamido-2,4,6-trideoxy-D,L-arabino-hexopyranose, a desmethyl analog of N-acetyl-L-hoTantosamine, the glycosidic residue of the cardenolide HoTarosine A and holantosines C and D, has been prepared via a novel intramolecular rearrangement of an amino alcohol and has been characterized by single-crystal X-ray diffraction.     

Analytical Determination of 1,6-Anhydro-β-D-Glucopyranose and Kinetic Studies Under Hydrothermal Conditions

1,6-Anhydro-β-D-giucopyranose was identified for the first time in aqueous solutions obtained by hydrothermolysis of cellulosic matter. The identification and quantitative determination of the 1,6-anhydro-β-D-glucopyranose, as well as of further degradation and conversion products, was accomplished by means of HPLC. For kinetic studies, 1,6-anhydro-β-D-glucopyranose was degraded in aqueous solution under hydrothermal conditions in the range of 200-240°C. A kinetic model covering both formation and decomposition of 1,6-anhydro-β-D-glucopyranose is proposed.     

Asymmetric Synthesis of Phosphinous Tungsten Complexes

Abstract

The asymmetric synthesis of phosphinous compounds from diheterophosphacycloal kane-1,3,2 was investigated in a transition metal complex series. Complexes 1 and 2 were prepared from diaminophosphine, (?)-ephedrine and W (CO)₅ THP (1: δ³¹ P=+147,6 ppm; J_PW=313 Hz M^.+=595;2 δ³ p=+156 ppm J_PW=304 Hz M^.+=533; 90%dp) in two steps. Methyl lithium reacted with 1 to give stereospecific 3 (83%Yield) by P-O linkage (3 δ³¹ P=+64 ppm; J_PW =261 Hz; M^.+ ? 28=583). The aminophosphine complex 3 was stereochemically stable and was used for studies of synthetic applications. HCL gas reacted with 3 in CH₂Cl₂ to give the non optically active chlorophosphine complex 4 (δ³¹ P=+103,6 ppm; J_PW=290 Hz; M^.+ =482). This compound immediately gave salt 6 (δ³¹ P=+66,7 ppm; J_PW =240 Hz) by reaction with (?)-menthol and triethylamine. The acid methanolysis of 3 gave a mixture of 5 and 6 and the unchanged (?)-ephedrine salt [5:30% yield; δ³¹ P=+114 ppm; J_pw=280 Hz; [α]_D=+1,2° (CH₂Cl₂); M^.+=478; 6 : 60% yield; δ³¹p=+102,9 ppm; J_PW=264 Hz; [α]_D =+16,9° (CH₂Cl₂); M^.+=464]. Compound 6 was thus obtained with a 80% yield and a specific rotation of + 20,2° (CH₂Cl₂) in isopropanol/H₂SO₄ 5M medium. The enantiomeric excess of 6 was determined by RMN³¹P. Acid hydrolysis of 3 or the reaction with CH₃SO₃H, gave phosphinous acid complex 6 with an optical rotation of + 4,8° or ?1,8° respectively. These results provide precious informations about the stereochemistry and reactivity of the P-N linkage in this aminophosphine transition metal series, which differs notably from that of the corresponding (PO) N bond.     

An Improved Total Synthesis of (±) - Podocarpic Acid by a Cyclialkylation Route

A number of total syntheses of (±) - podocarpic acid (i) have been described¹ King, King and Topliss² first identified one of the products from nonstereo-selective cyclization of (4) with polyphosphoric acid as (±)- ethyl-O-methylpodocarpate (2) and correlated that with the corresponding acid (3), prepared in an extremly poor yield (ca 0.4%)³ by Bhattacharyya³, and Haworth and Moore⁴ by cyclization of (5) with a mixture of sulfuric acid and acetic acid. More recently Mancini, Fringuelli and Taticchi⁵ prepared (3) (in 4.8% yield) by repeating Howorth¹ s cyclization of (4). In continuation of our studies on cyclialky-     

An Unusual Behavior of Methyl or Benzyl 3-Azido-5-O-Benzoyl-3,6-Di-Deoxy-α-L-Talofuranoside with (Dimethylamino)Sulfur Trifluoride; Migration of the Alkoxyl Group from the C-1 to the C-2 Position

The reaction of methyl or benzyl 3-azido-5-0-benzoyl-3,6-di-deoxy-α-L-talofuranoside with (diethylamino)sulfur trifluoride (DAST) in toluene at 60°C resulted in the formation of 3-azido-5-0-benzoyl-3,6-dideoxy-2-0-methyl (or 2-0-benzyl)-3β-L-galactofuranosyl fluoride in good yield. In this reaction the alkoxyl group at C-1 migrated to the C-2 position and a fluorine atom entered into the C-1 position. The furanosyl fluoride was converted, via reduction of the azido group followed by N-trifluoroacetylation, acetolysis, and O-deacetylation, into 3,6-dideoxy-2-0-methyl-3-trifluoroacet-amido-L-galactopyranose (2-methoxy-Daunosamine derivative).     

Spontaneous Aromatization of Diels-Alder Adducts in the Reaction of Alkatrienyl Phosphonates with Alkyl Esters of Acetylencarboxylic Acids

Abstract

The subject of this study was the Diels-Alder reaction involving dialkyl (3-methylpenta-1,2,4-trienyl)phosphonates1a-d, dialkyl(5-methyl-hexa-1,3,4-trienyl)phosphonates 2a-b, and dienophiles (esters of acetylencarboxylic acids) 3a-c, at 65–90°C, in chloroform or with no solvent. The reaction between 1a-d and 3a-b led to the benzyl phosphonates 4a-h, while with 3c it proceeds to a mixture of 5a-d (90%) and 6a-d (10%), which are dialkyl esters of the 3-carboalkoxy(or 2-carboalkoxy)-6-methyl-benzyl phosphonic acid. The intermediate Diels-Alder adducts (A) are not even spectroscopically observable, i.e. in the course of the reaction a 1,5-sigmatropic isomerization occurs, accompanied by aromatization of (A). The isomerization is spontaneous: at ambient temperature 1a-d and 3a-b react slowly and form aromatic compounds:     

Peptide Formation by Aminolysis of 1-Thio-β-D-glucopyranosyl Esters of N-Acylaminoacids

Abstract

The susceptibility of the fully acetylated 1-thio–β-D-glucopyranosyl esters of N-protected amino acids toward the amino group of an external amino acid-or peptide-ester was examined in dichloromethane at room temperature and at 40°, respectively. In each case, the aminolysis reaction led to rupture of the C-1 thiolester bond and formation of the corresponding N-acylpeptide ester; the reaction proceeded without racemization of the aglycon chiral centre. Evidence for a remarkably high acylating efficiency of the sugar—amino acid C-1 thiolester bond is presented.     

Studies on the Conformation of Polyhydroxyalkylpyrazolo (3,4-b) Quinoxalines

¹H NMR spectral studies on polyhydroxyalkylpyrazolo-(3,4-b)-quinoxaline derivatives of sugars having five to seven carbon atoms have shown that the polyhydroxyalkyl chain exists in a conformation in which a hydrogen bond is formed between the l'-hydroxyl group and N-2 of the pyrazolo(3,4-b)-quinoxaline base moiety. The polyhydroxyalkyl chain exists in the planar zigzag conformation, where no 1,3 syn axial interaction is present. Substitution in the base moiety did not change the extent of the population of the planar zigzag conformation.     

Aqueous Polymerization of Methyl Methacrylate Initiated by the Potassium Bromate-Thiomalic Acid Redox System

The redox system composed of potassium bromate and thiomalic acid was used to initiate the aqueous polymerization of methyl methacrylate under nitrogen atmosphere at 35 ± 0.2°C. The initial rates of polymerization have been found to be approximately proportional to the first power of the initiator concentration in the range of 2.5 to 6.0 ± 10^?3 M and to the first power (1.15) of monomer concentration in the range of 3.72 to 11.16 ± 10^?2 M The overall rate was independent of activator concentration, approaching a maximum at 10 × 10^?3 M. The overall energy of activation was found to be 8.80 kcal/mol. The initial rate and the maximum conversion attained a maximum value at 35°C in the temperature range of 20 to 45°C.     

Phosphorus Compounds of Polyols. Unusual Equilibria Connecting Bicyclic Phosphites and Polycyclic Phosphoranes

Abstract

Threitol or (and) xylitol react with hexamethylphosphorus triamide giving bicyclic phosphites 1, 2, whose structure has been established by NMR spectroscopy. These compounds undergo, at 60°C, fast oligornerisation leading, particularly, to polycyclic phosphoranes 3,4. In presence of diethylamine 3, 4 give again phosphites 1,2.     

Use of the Rotated Ring Disc Electrode for the Analytical Determination of Dithiaalcanediols in Aquo-Alcoholic Media and Its Rate of Oxidation with Bromine

Abstract

We used bromine generated and detected on the ring-dise electrode for the titration of aquo-alcoholic solution of dithiaalcanediol. The analysis of the ring current vs disc current curve provided a means of determination of the rate constant k of the second order homogeneous and fast reaction of bromine with each of the two sulfide groups of dithiaalcanediol. A value of (3+1)× 10^?6M^?1 _s ^?1 was found for k at 25°C.     

Solvolysis of 9-Bromo-ω-bromolongifolene/9-bromo-longifolene: Synthesis of Longi-β-Nozigiku Alcohol/Longicyclenyl Alcohol from Japanese Sugi/Hinoki Essential Oils

Longi-β-nozigiku alcohol 3/longicyclenyl alcohol 4 reported in Japanese sugi/hinoki essential oils, have been synthesized from longicyclene 2 using bromination as the key step. 9-Bromo-ω-bromo longifolene 5 (prepared from 2 by action of pyridine perbromide) is exposed to silver perchlorate in aqueous acetone to afford the ω-bromo-alcohol 7; refluxing 3. with Na-t-BuoH-THF gives the homoallylic alcohol 3. Solvolysis of 9-bromolongifolene 6 (prepared by bromination of 2 with NBS in CHCl₃ at reflux) with KOAc in ACOH at 75°/4 hr followed by hydrolysis furnishes longicyclenyl alcohol 4.     

An Efficient and Unambiguous Synthesis of 2-Hydroxymethyl-1, 3-Propanediol

In 1949, Fujui³ reported the synthesis of what was presumed to be 2-hydroxymethyl-1, 3-propanediol (4) in 70% yield by the condensation of acetaldehyde with formaldehyde (1:2.5 molar ratio) in the presence of calcium hydroxide, and subsequent catalytic hydrogenation over a nickel catalyst. The product was reported to have a melting point of 182°. In 1955, the triester tris-(carbethoxy) methane (5) was reduced with lithium aluminum hydride to give a product with a reported melting point of 58–62°; the yield was only 5%.⁴ Owing to the conflicting data in the literature and the vast potential of 4; we have developed an efficient and unambiguous route to 4; this scheme is also adaptable to clean conversions to mono-, di- and tri-O-substituted derivatives of 4: