四川乌龙茶香气化学成分的剖析

四川乌龙茶在低温减压蒸馏所得香气浓缩物经气相色谱-质谱联用测定,以气相色谱保留值验证,鉴定出19个化合物,它们是:丙酮,乙酸乙酯,顺-3-己烯醇-[1],乙酸顺-3-己烯酯,苯甲醇,反-芳樟醇氧化物(呋喃型),顺-芳樟醇氧化物(呋喃型),芳樟醇,苯乙醇,反-芳樟醇氧化物(吡喃型),丁酸顺-3-己烯酯,香叶烯,己酸顺-3-己烯酯,茉莉酮,橙花叔醇,金台欢醇,茉莉酮酸甲酯,正十六烷和2,6,10,14-四甲基十五烷。     

Stereoselective total synthesis of cis- and trans-3-hydroxypipecolic acid

[reaction: see text] 3-Hydroxypipecolic acid, a nonproteinogenic cyclic alpha-amino acid, is a common structural moiety found in a large number of natural and synthetic compounds of medicinal significance. Utilizing D-serine as a chiral template, the present research describes efficient and straightforward routes to cis- and trans-3-hydroxypipecolic acids in enantiopure form. The key steps in the syntheses involve chelation-controlled addition of a homoallyl Grignard reagent to a protected serinal derivative toward stereoselective formation of the corresponding syn-amino alcohol adduct 3. On the other hand, zinc borohydride-mediated chelation-controlled reduction of a serine-derived alpha-aminoketone precursor leads to the formation of the corresponding anti-amino alcohol adduct 4 with high stereoselectivity. Following an efficient sequence of reactions, the above amino alcohol derivatives were subsequently transformed to the corresponding cis- and trans- title compounds, respectively.     

Total synthesis of flocoumafen via knoevenagel condensation and intramolecular ring cyclization: general access to natural products

The total synthesis and structure determination of cis- and trans-flocoumafen was described. The key synthetic steps involve Knoevenagel condensation with p-methoxybenzaldehyde, in situ decarboxylation and intramolecular ring cyclization to construct the tetralone skeleton. Stereospecific reduction of the O-alkylated ketone 13 afforded good yield of precusor alcohol 5. Final coupling of alcohol 5 with 4-hydroxy-coumarin yielded flocoumafen (1). Separation and structure determination of cis- and trans-flocoumafen through 2D NMR analyses-assisted computer simulation techniques for the evaluation of anticoagulant activities are reported for the first time. This method is useful for generating the core tetralone skeleton of 4-hydroxycoumarin derivatives and provides a generalized access to various warfarin type anticoagulants.     

Synthesis of cis- and trans-3-aminocyclohexanols by reduction of β-enaminoketones

We describe a protocol developed for the preparation of β-enaminoketones derived from 1,3-cyclohexanediones, and their subsequent reduction by sodium in THF-isopropyl alcohol to afford cis- and trans-3-aminocyclohexanols.     

Hydrometallation of 1-alkyl-3-trifluoromethyl propargyl alcohols

The hydrometallation of trifluoromethylated propargyl alcohol derivatives with metal hydride reagents proceeds smoothly to give cis- and trans-olefins on H₂O quenching. The halodemetallation of intermediate formed in the reaction process was also examined.     

The skeletal rearrangement of gold- and platinum-catalyzed cycloisomerization of cis-4,6-dien-1-yn-3-ols: pinacol rearrangement and formation of bicyclo[4.1.0]heptenone and reorganized styrene derivatives

With gold and platinum catalysts, cis-4,6-dien-1-yn-3-ols undergo cycloisomerizations that enable structural reorganization of cyclized products chemoselectively. The AuCl3-catalyzed cyclizations of 6-substituted cis-4,6-dien-1-yn-3-ols proceeded via a 6-exo-dig pathway to give allyl cations, which subsequently undergo a pinacol rearrangement to produce reorganized cyclopentenyl aldehyde products. Using chiral alcohol substrates, such cyclizations proceed with reasonable chirality transfer. In the PtCl2-catalyzed cyclization of 7,7-disubstituted cis-4,6-dien-1-yn-3-ols, we obtained exclusively either bicyclo[4.1.0]heptenones or reorganized styrene products with varied substrate structures. On the basis of the chemoselectivity/structure relationship, we propose that bicyclo[4.1.0]heptenone products result from 6-endo-dig cyclization, whereas reorganized styrene products are derived from the 5-exo-dig pathway. This proposed mechanism is supported by theoretic calculations.     

PHOTOOXIDATION OF CITRONITRILE

Photooxidation of citronitrile followed by esterification gives two new perfume prod-ucts: acetic esters of 2-methyl-6-formyl-1, 5-dieneheptanol-3 and 7-cyano-2, 6-dimethyl-3,6-dieneheptanol-2. The content of the secondary alcohol isomer in -ene type reaction ofcitronitrile has been found to be extremely low. Formation of 2-formyltetrahydrofuran, theprecursor of 2-methyl-6-formyl-1,5-diene-3-heptyl acetate, might proceed via ketoneoxidation mechanism of the secondary alcohol. In order to confirm the proposed mechanism,the disappearance rate constants of citronitrile, linalool acetate have been determined by com-parison with the photooxidation rate constant of 2,3-diphenyl-p-hexadioxene-2. A tetrapterouscorrelation diagram of C-2 double bond photooxidation of cis- and trans-citronitriles has beenused to interpret our observations. The difference in the rate constants of cis- and trans-citronitriles provides new evidence supporting the stepwise mechanism of -ene type reactionof singlet oxygen.     

Total synthesis of (-)-cassine

The PdCl(2)-catalyzed cyclization of amino allylic alcohol 16 gave the cyclized product 17a with excellent diastereoselectivity. The versatility of compound 17a as the building block for synthesizing cis-2,6-disubstituted piperidine alkaloids has been demonstrated by a total synthesis of (-)-cassine (1). [reaction--see text]     

Two general routes to 1,4-disubstituted-2,3,4,5-tetrahydro- 1H-3-benzazepines

[structure] Two general routes to 1,4-disubstituted-2,3,4, 5-tetrahydro-1H-3-benzazepines are described. Both routes utilize an appropriately functionalized phenethylamino alcohol as the penultimate intermediate: the first route makes use of the reductive amination of a benzyl alkyl ketone with alpha-(aminomethyl)benzyl alcohol, while the second route utilizes the addition of a Grignard reagent to the oxazolidine derived from a substitued phenylacetaldehyde and alpha-(methylaminomethyl)benzyl alcohol. In all cases studied, the cis-1,4-disubstituted-2,3,4, 5-tetrahydro-1H-3-benzazepine was obtained as the major product.     

Gas-Liquid Chromatographic Analysis of Mixtures of Cis- and Trans-Crotyl Alcohol in Commercial Samples and in the Products of Controlled Potential Electrolysis of Crotonaldehyde

Abstract

G. L. C. enabled a separation of cis- and trans-crotyl alcohol. Commercially available samples of crotyl alcohol and the products of controlled potential electrolysis of crotonaldehyde contained about 20% of the cis-form. The limited amount of information available on N. M. R. spectra of similar compounds prevented an application of the coupling constants for the interaction between a methyl group and ethylenic protons in attribution of the trans-structure. Attribution of trans-structure to the predominant form was based upon I. R. spectra and synthesis of the trans-isomer.     

Low-temperature X-ray structural studies of the ester and ether derivatives of cis- and trans-4-tert-butyl cyclohexanol and 2-adamantanol: application of the variable oxygen probe to determine the relative sigma-donor ability of C-H and C-C bonds

Results of low-temperature X-ray structural studies for five cis-, and three trans-4-tert-butyl cyclohexanol, and six 2-adamantanol ester and ether derivatives are reported. Plots of C-OR bond distance against pKa(ROH) for derivatives of axial alcohol (5), equatorial alcohol (6) and 2-adamantanol derivatives (7) give slopes of -2.77 x 10(-3), -2.86 x 10(-3) and -3.05 x 10(-3), respectively. Given that the relative differences in the slopes are modest, no clear distinction can be made about the relative sigma-donor ability of a C-H bond and a C-C bond.     

Synthesis of the acetate of octadeca-trans-2,cis-13-dien-1-ol,a component of the sex pheromones of Synanthedon tipuliformis and Zeuzera pyrina

A new synthesis of the acetate of octadeca-trans-2,cis-13-dien-1-ol based on the alkylation of propargyl alcohol with pentadec-cis-10-enyl bromide, obtained from the readily accessible decamethylene bromohydrin, has been effected.All-Union Scientific-Research Institute of Biological Methods of Plant Protection, Kishinev. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 264–266, March–April, 1989.     

Synthesis and structure of [Zn(OMe)(L)] x [Zn(OH)(L)] x 2(BPh4), L = cis,cis-1,3,5-tris[(E,E)-3-(2-furyl)acrylideneamino]cyclohexane: structural models of carbonic anhydrase and liver alcohol dehydrogenase

Direct reaction of [Zn(OH)(L)]+, L = cis,cis-1,3,5-tris[(E,E)-3-(2-furyl)acrylideneamino]cyclohexane, with methanol gives a mixture of the starting material and [Zn(OMe)(L)]+; structural analysis of the complexes shows that they are models of reactive intermediates in the catalytic cycles of the zinc enzymes carbonic anhydrase and liver alcohol dehydrogenase.     

Phosphino-aminothiazoline platinum(II) and platinum(II)/gold(I) complexes: structural, chemical and vapoluminescent properties

Phosphino-amino-thiazolines and -thiazoles can exist in solution in two tautomeric forms, in which the N-H proton involves the endo-cyclic or exo-cyclic nitrogen atom. The two tautomers show different reactivities toward alcoholysis; the imino form degrades more rapidly. Their bischelated platinum complexes were studied in the solid state by single crystal X-ray diffraction. Thus, the unique stereoelectronic features of the [Pt(PN(th))] (PN(th)=diphenylposphino-aminothiazoline) moiety were revealed. The complex cis-[Pt(PN(th))(2)] reacts with gold(I) salts to yield dimetallic compounds, the molecular structures of which have been determined by X-ray diffraction. Solid cis-[Pt(PN(th))(2)] shows vapoluminescent properties if exposed to alcohol vapors. A combined photophysical and crystallographic investigation has been carried out to clarify the unprecedented rigidochromic role of the alcohol in this phenomenon.     

Chemical behavior of the biradicaloid (HO...ONO) singlet states of peroxynitrous acid. The oxidation of hydrocarbons, sulfides, and selenides

Various high levels of theory have been applied to the characterization of two higher lying biradicaloid metastable singlet states of peroxynitrous acid. A singlet minimum (cis-2) was located that had an elongated O-O distance (2.17 A) and was only 12.2 kcal/mol [UB3LYP/6-311+G(3df,2p)+ZPVE] higher in energy than its ground-state precursor. A trans-metastable singlet (trans-2) was 10.9 kcal/mol higher in energy than ground-state HO-ONO. CASSCF(12,10)/6-311+G(d,p) calculations predict the optimized geometries of these cis- and trans-metastable singlets to be close to those obtained with DFT. Optimization of cis- and trans-2 within the COSMO solvent model suggests that both exist as energy minima in polar media. Both cis- and trans-2 exist as hydrogen bonded complexes with several water molecules. These collective data suggest that solvated forms of cis-2.3H(2)O and trans-2.3H(2)O represent the elusive higher lying biradicaloid minima that were recently (J. Am. Chem. Soc. 2003, 125, 16204) advocated as the metastable forms of peroxynitrous acid (HOONO). The involvement of metastable trans-2 in the gas phase oxidation of methane and isobutane is firmly established to take place on the unrestricted [UB3LYP/6-311+G(d,p)] potential energy surface (PES) with classical activations barriers for the hydrogen abstraction step that are 15.7 and 5.9 kcal/mol lower than the corresponding activation energies for producing products methanol and tert-butyl alcohol formed on the restricted PES. The oxidation of dimethyl sulfide and dimethyl selenide, two-electron oxidations, proceeds by an S(N)2-like attack of the heteroatom lone pair on the O-O bond of ground-state peroxynitrous acid. No involvement of metastable forms of HO-ONO was discernible.     

Absolute asymmetric synthesis of "chiral-at-metal" Grignard reagents and transfer of the chirality to carbon

Two new six-coordinate Grignard reagents, cis-[(p-CH(3)C(6)H(4))MgBr(dme)(2)] (1) and cis-[MgCH(3)(thf)(dme)(2)]I (2), have been synthesized and their crystal structures have been determined. Both reagents are cis-octahedral and therefore chiral. They crystallize as conglomerates and racemize rapidly in solution. By utilizing these properties, the absolute asymmetric synthesis of specifically the Delta or the Lambda enantiomer was achieved for both Grignard reagents. Enantiopure 1 and 2 were then reacted with butyraldehyde or benzaldehyde to give the corresponding alcohol in up to 22 % enantiomeric excess. At -60 degrees C, the Grignard reagents crystallize as racemic phases instead of conglomerates. Consequently, the crystal structures of rac-cis-[(p-CH(3)C(6)H(4))MgBr(dme)(2)].DME (3) and rac-cis-[MgCH(3)(thf)(dme)(2)]I (4) could be determined.     

Synthesis and stereochemistry of 1-alkyl-2-methoxycarbonyl-3-phenylaziridines

Mixtures of cis- and trans-1-alkyl-2-methoxycarbonyl-3-phenylaziridines are formed in the reaction of methyl -bromocinnmate with excess amine, amino alcohol, and amino acid methyl ester hydrochloride. The ratios of the isomers depend on the solvent used.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 937–939, July, 1980.     

Stereochemistry of ethynylation,normant, and grignard reactions in the 1-alkyldecahydro-4-quinolone series

The different stereochemistries of the addition of acetylene and vinyl- or ethylmagnesium bromides to 1-alkyl- and 1,2,2-trimethyl-trans-decahydro-4-quinolones are shown. In the ethynylation of mixtures of cis- and trans-1-alkyldecahydro-4-quinolones, one acetylenic alcohol of the cis series was isolated in each case in addition to two epimeric (with respect to the 4 position) trans alcohols. The configurations of the synthesized alcohols were established by IR spectroscopy.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1529–1536, November, 1976.     

Effect of electronic interactions on NMR 1J(CF) and 2J(CF) couplings in cis- and trans-4-t-butyl-2-fluorocyclohexanones and their alcohol derivatives

In order to study the influence of hyperconjugative, inductive, steric, and hydrogen-bond interactions on (1)J(CF) and (2)J(CF) NMR spin-spin coupling constants (SSCCs), they were measured in cis- and trans-4-t-butyl-2-fluorocyclohexanones and their alcohol derivatives. The four isotropic terms of those SSCCs, Fermi contact (FC), spin dipolar (SD), paramagnetic spin-orbit (PSO), and diamagnetic spin-orbit (DSO), were calculated at the SOPPA(CCSD)/EPR-III level. Significant changes in FC and PSO terms along that series of compounds were rationalized in terms of their transmission mechanisms by employing a qualitative analysis of their expressions in terms of the polarization propagator formalism. The PSO term is found to be sensitive to proximate interactions like steric compression and hydrogen bonding; we describe how it could be used to gauge such interactions. The FC term of (2)J(CF) SSCC in cis-4-t-butyl-2-fluorocyclohexanone is rationalized as transmitted in part by the superposition of the F and O electronic clouds.     

Cumene oxidation by cis-[RuIV(bpy)2(py)(O)]2+, revisited

cis-[RuIV(bpy)2(py)(O)]2+ oxidizes cumene (2-phenylpropane) in acetonitrile solution primarily to cumyl alcohol (2-phenyl-2-propanol), alpha-methylstyrene, and acetophenone. Contrary to a prior report, the rate of the reaction is not accelerated by added nucleophiles. There is thus no evidence for the hydride transfer mechanism originally proposed. Instead, the results are consistent with a mechanism of initial hydrogen atom transfer from cumene to the ruthenium oxo group. This is indicated by the correlation of rate with C-H bond strength and by the various products observed. The formation of acetophenone, with one carbon less than cumene, is suggested to occur via a multistep pathway involving decarbonylation of the acyl radical from 2-phenylpropanal. An alternative mechanism involving beta-scission of cumyloxyl radical is deemed unlikely because of the difficulty of generating alkoxyl radicals under anaerobic conditions and the lack of rearranged products in the oxidation of triphenylmethane by cis-[RuIV(bpy)2(py)(O)]2+.