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1.
Myong Sang Kim 《Tetrahedron letters》2005,46(20):3545-3548
β-CF3-α,β-diphenylvinyl sulfide 3a was prepared stereoselectively in 77% yield from the reaction of 2 with phenyllithium at room temperature for 5 h. Oxidation of 3a with MCPBA afforded the corresponding vinyl sulfone 4a, in which (E)-4a can be crystallized in a mixture of CH2Cl2 and hexane. The addition-elimination reaction of (E)-4a with phenyllithium having substituents on the benzene ring provided 5a-j in 51-82% yields stereospecifically. Similarly, the treatment of (E)-4a with p-chloroethoxyphenyllithium in the presence of 12-crown-4 (20 mol %) at −10 °C, followed by slowly warming to room temperature, resulted in the formation of the corresponding panomifene precursor 6 in 82% yield. 相似文献
2.
Isotachysterol, the acid-catalyzed isomerization product of vitamin D3, produces seven previously unknown oxygenation products in a self-initiated autoxidation reaction under atmospheric oxygen in the dark at ambient temperature. They are (5R)-5,10-epoxy-9,10-secocholesta-6,8(14)-dien-3β-ol (6a), (5S)-5,10-epoxy-9,10-secocholesta-6,8(14)-dien-3β-ol (6b), (10R)-9,10-secocholesta-5,7,14-trien-3β,10-diol (7a), (10S)-9,10-secocholesta-5,7,14-trien-3β,10-diol (7b), (7R,10R)-7,10-epoxy-9,10-secocholesta-5,8(14)-dien-3β-ol (8), 5,10-epidioxyisotachysterol (9) and 3,10-epoxy-5-oxo-5,10-seco-9,10-secocholesta-6,8(14)-dien-10-ol (10). The formation of these products is explained in terms of free radical peroxidation chemistry. 相似文献
3.
Jungui DaiShujun Zhang Jun-ichi SakaiJiao Bai Yoshiki OkuMasayoshi Ando 《Tetrahedron letters》2003,44(5):1091-1094
Three C-14 oxygenated taxanes, 2α,5α,10β,14β-tetraacetoxytaxa-4(20),11-diene (1), 2α,5α,10β-triacetoxy-14β-(2-methylbutyryloxy)taxa-4(20),11-diene (2), and yunanaxane (3), major products of callus cultures of Taxus spp., were regio- and stereoselectively hydroxylated at the 7β position by a fungus, Absidia coerulea IFO 4011. Intriguingly, when 1 was co-administered with β-cyclodextrin and incubated with the fungus cell cultures, three other compounds 5α,9α,10β,13α-tetraacetoxytaxa-4(20),11-dien-14β-ol (7), 5α,9α,10β,13α-tetraacetoxytaxa-4(20),11-dien-1β-ol (8) and 5α,9α,10β,13α-tetraacetoxy-11(15→1) abeotaxa-4(20),11-dien-15-ol (9) were obtained. 相似文献
4.
Taxuyunnanine C (1) and its analogs (2 and 3), the C-14 oxygenated 4(20), 11-taxadienes from callus cultures of Taxus sp., were regio- and stereo-selectively hydroxylated at the 7β position by a fungus, Abisidia coerulea IFO 4011, and it was interesting that the longer the alkyl chain of the acyloxyl group at C-14 became, the higher the yield of 7β-hydroxylated product was. Besides the three 7β-hydroxylated products (5, 9, 17), other nine new products (7, 11, 12, 14, 15, 16, 18, 20 and 21) and six known products (4, 6, 8, 10, 13 and 19) were obtained. Subsequently, the acetylated derivatives (24 and 27) of 7β-and 9α-hydroxylated products of 1 were regio- and stereo-specifically hydroxylated at the 9α position by Ginkgo cells and 7β position by A. coerulea, respectively. Thus, the two specific oxidations have been combined. These bioconversions would provide not only valuable intermediates for the semi-synthesis of paclitaxel or other bioactive taxoids from 1 and its analogs, but also some useful hints for the biosynthetic pathway of taxoid in the natural Taxus plant. 相似文献
5.
Novel reactions of lycoctonine analogs: unusual pyrolysis of C4-COOH and hydrogenolysis of N-C6 bond
Pyrolysis of carboxylic acid group at C-4 of 2, an oxidation product from the C19-diterpenoid alkaloid lycoctonine 1, generated an unexpected but novel rearranged product 13 (37%). The structure of 13 was confirmed by its 2D NMR data and its single crystal X-ray crystallographic analysis. In addition, hydrogenolysis of 13 in the presence of acetic acid yielded the N-C6 bond fission products 16 and 17, which represents the first hydrogenolysis involving the breakage of the N-C6 bond of the diterpenoid alkaloids. Some new observations on the oxidation of lycoctonine 1 were described as well. 相似文献
6.
The key intermediate 1,2:5,6-di-O-isopropylidene-3-deoxy-3β-allyl-α-d-glucofuranose (8) could be conveniently prepared through radical induced allyl substitution at C-3 of appropriate 1,2:5,6-di-O-isopropylidene-α-d-glucofuranose derivatives (7a,b) and used to synthesize enantiomeric bishydroxymethyl aminocyclopentanols 13 and 19 by the application of a 1,3-dipolar nitrone cycloaddition reaction involving the C-5 or C-1 aldehyde functionality. The products were subsequently transformed into carbanucleoside enantiomers 15 and 21. The diastereomeric isoxazolidinocyclopentane derivative 20 was similarly converted to carbanucleoside 22. 相似文献
7.
The reaction of a rhodanine derivative (=(Z)-5-benzylidene-3-phenyl-2-thioxo-1,3-thiazolidin-4-one; 1) with (S)-2-methyloxirane (2) in the presence of SiO2 in dry CH2Cl2 for 10 days led to two diastereoisomeric spirocyclic 1,3-oxathiolanes 3 and 4 with the Me group at C(2) (Scheme 2). The analogous reaction of 1 with (R)-2-phenyloxirane (5) afforded also two diastereoisomeric spirocyclic 1,3-oxathiolanes 6 and 7 bearing the Ph group at C(3) (Scheme 3). The structures of 3, 4, 6, and 7 were confirmed by X-ray crystallography (Figs. 1 and 2). These results show that oxiranes react selectively with the thiocarbonyl group (CS) in 1. Furthermore, the nucleophilic attack of the thiocarbonyl S-atom at the SiO2-activated oxirane ring proceeds with high regio- and stereoselectivity via an SN2-type mechanism. 相似文献
8.
Two β-cyclodextrin-C60 conjugates (3 and 4) with a flexible linker at the secondary face of cyclodextrin are synthesized by a single reaction of 2-(ω-azidoundecanyl)-2-O-heptakis (2,3,6-tri-O-methyl)-β-cyclodextrin (2) and C60, both of which display satisfactory water solubility. Structural analyses show that 3 is a closed [5,6] aziridinofullerene, whereas 4 is a bis-adduct derivative. Using rhodamine B (RhB) as a guest molecule, the inclusion complexation behavior of 3 was investigated in aqueous solution. 相似文献
9.
Lili Ning Jixun ZhanGuiqin Qu Lei ZhongHongzhu Guo Kaishun BiDean Guo 《Tetrahedron》2003,59(23):4209-4213
Biotransformation of triptolide 1 by Cunninghamella blakesleana (AS 3.970) was carried out. Seven biotransformation products were obtained and four of them were characterized as new compounds. On the basis of their NMR and mass spectral data, their structures were characterized as 5α-hydroxytriptolide 2, 1β-hydroxytriptolide 3, triptodiolide 4, 16-hydroxytriptolide 5, triptolidenol 6, 19α-hydroxytriptolide 7 and 19β-hydroxytriptolide 8. All the new transformed products (2, 3, 7 and 8) were found to exhibit potent in vitro cytotoxicity against some human tumor cell lines. 相似文献
10.
The microbiological transformation of polyphyllin I (compound I), polyphyllin III (compound II), polyphyllin V (compound III) and polyphyllin VI (compound IV) by Curvularia lunata into their corresponding subsaponins, for example, diosgenin-3-O-α-l-arabinofuranosyl (1→4)-β-d-glucopyranoside (compound V), diosgenin-3-O-α-l-rhamnopyranosyl (1→4)-β-d-glucopyranoside (compound VI), diosgenin-3-O-β-d-glucopyranoside (compound VII) and pennogenin-3-O-β-d-glucopyranoside (compound VIII), were studied in this paper. Curvularia lunata is able to hydrolyze terminal rhamnosyls that are linked by 1→2 C- bond to sugar residues of steroidal saponins at C-3 position with high activity and regioselectivity. 相似文献
11.
(Z)-5-(2-(1H-Indol-3-yl)-2-oxoethylidene)-3-phenyl-2-thioxothiazolidin-4-one (7a-q) derivatives have been synthesized by the condensation reaction of 3-phenyl-2-thioxothiazolidin-4-ones (3a-h) with suitably substituted 2-(1H-indol-3-yl)-2-oxoacetaldehyde (6a-d) under microwave condition. The thioxothiazolidine-4-ones were prepared from the corresponding aromatic amines (1a-e) and di-(carboxymethyl)-trithiocarbonyl (2). The aldehydes (6a-h) were synthesized from the corresponding acid chlorides (5a-d) using HSnBu3. 相似文献
12.
Artem M. Abakumov Marta D. Rossell Sergey Yu. Vassiliev Gustaaf Van Tendeloo 《Journal of solid state chemistry》2006,179(2):421-428
Phase transitions in the elpasolite-type K3AlF6 complex fluoride were investigated using differential scanning calorimetry, electron diffraction and X-ray powder diffraction. Three phase transitions were identified with critical temperatures , and . The α-K3AlF6 phase is stable below T1 and crystallizes in a monoclinic unit cell with a=18.8588(2)Å, b=34.0278(2)Å, c=18.9231(1)Å, β=90.453(1)° (a=2ac−cc, b=4bc, c=ac+2cc; ac, bc, cc—the basic lattice vectors of the face-centered cubic elpasolite structure) and space group I2/a or Ia. The intermediate β phase exists only in very narrow temperature interval between T1 and T2. The γ polymorph is stable in the T2<T<T3 temperature range and has an orthorhombic unit cell with a=36.1229(6)Å, b=17.1114(3)Å, c=12.0502(3)Å (a=3ac−3cc, b=2bc, c=ac+cc) at 250 °C and space group Fddd. Above T3 the cubic δ polymorph forms with ac=8.5786(4)Å at 400 °C and space group . The similarity between the K3AlF6 and K3MoO3F3 compounds is discussed. 相似文献
13.
l-N-Formyl tryptophan methyl ester (3) underwent a Bischler-Napieralski reaction with POCl3 at room temperature or under microwave irradiation, resulting in the unusual formation of β-carboline dimers 5 and 6. Most importantly, acetylation using Ac2O of each of the dimers 5 and 6 separately afforded 1-[3′-carbomethoxy-β-carbolinyl]-3-carbomethoxy-9-acetyl-β-carboline (7) as the only product, the structure of which was confirmed by X-ray crystallography studies. 相似文献
14.
《Tetrahedron》2004,60(36):7921-7932
The microbiological transformation of 13α,17-dihydroxy-stemodane (2) by the fungus Mucor plumbeus afforded 13α,17,19-trihydroxy-stemodane (3), 3β,13α,17-trihydroxy-stemodane (5), 3-oxo-13α,17-dihydroxy-stemodane (7), 7α,13α,17,19-tetrahydroxy-stemodane (8), 3β,11α,13α,17-tetrahydroxy-stemodane (10), 3β,7α,13α,17-tetrahydroxy-stemodane (12), 3β,8β,13α,17-tetrahydroxy-stemodane (14), 2α,13α,17-trihydroxy-stemodane (16), 2α,13α,17,19-tetrahydroxy-stemodane (17), 2α,3β,13α,17-tetrahydroxy-stemodane (20) and 3β,11β,13α,17-tetrahydroxy-stemodane (22), whilst the incubation of 13α,14-dihydroxy-stemodane (25) gave 3β,13α,14-trihydroxy-stemodane (28), 2α,13α,14-trihydroxy-stemodane (29) and 13α,14,19-trihydroxy-stemodane (30). Preference for hydroxylations of ring A at C-2(α), C-3(β) and C-19 were observed in both incubations. An interesting rearrangement of 13α,14α-dihydroxy-stemodanes to 14-oxo derivatives with an unusual carbon framework has been observed under acetylation conditions. We have named this skeleton prestemodane, which, as a hydrocarbon ion, had been postulated as a biogenetic precursor of stemodane. 相似文献
15.
The two new compounds, Sr4Cu3(AsO4)2(AsO3OH)4·3H2O (1) and Ba2Cu4(AsO4)2(AsO3OH)3(2), were synthesized under hydrothermal conditions. They represent previously unknown structure types and are the first compounds synthesized in the systems SrO/BaO-CuO-As2O5-H2O. Their crystal structures were determined by single-crystal X-ray diffraction [space group C2/c, a=18.536(4) Å, b=5.179(1) Å, c=24.898(5) Å, β=93.67(3)°, V=2344.0(8) Å3, Z=4 for 1; space group P42/n, a=7.775(1) Å, c=13.698(3) Å, V=828.1(2) Å3, Z=2 for 2]. The crystal structure of 1 is related to a group of compounds formed by Cu2+-(XO4)3− layers (X=P5+, As5+) linked by M cations (M=alkali, alkaline earth, Pb2+, or Ag+) and partly by hydrogen bonds. In 1, worth mentioning is the very short hydrogen bond length, D···A=2.477(3) Å. It is one of the examples of extremely short hydrogen bonds, where the donor and acceptor are crystallographically different. Compound 2 represents a layered structure consisting of Cu2O8 centrosymmetric dimers crosslinked by As1φ4 tetrahedra, where φ is O or OH, which are interconnected by Ba, As2 and hydrogen bonds to form a three-dimensional network. The layers are formed by Cu2O8 centrosymmetric dimers of CuO5 edge-sharing polyhedra, crosslinked by As1O4 tetrahedra. Vibrational spectra (FTIR and Raman) of both compounds are described. The spectroscopic manifestation of the very short hydrogen bond in 1, and ABC-like spectra in 2 were discussed. 相似文献
16.
A.-K. Larsson R.L. Withers J.D. Fitz Gerald B.J. Kennedy 《Journal of solid state chemistry》2008,181(8):1816-1823
The P63 (a=2ap, b=2bp, c=cp) crystal structure reported for BaAl2O4 at room temperature has been carefully re-investigated by a combined transmission electron microscopy and neutron powder diffraction study. It is shown that the poor fit of this P63 (a=2ap, b=2bp, c=cp) structure model for BaAl2O4 to neutron powder diffraction data is primarily due to the failure to take into account coherent scattering between different domains related by enantiomorphic twinning of the P6322 parent sub-structure. Fast Fourier transformation of [0 0 1] lattice images from small localized real space regions (∼10 nm in diameter) are used to show that the P63 (a=2ap, b=2bp, c=cp) crystal structure reported for BaAl2O4 is not correct on the local scale. The correct local symmetry of the very small nano-domains is most likely orthorhombic or monoclinic. 相似文献
17.
TiO2 nanoparticles were modified with porphyrin derivatives, 5-[4-benzoic acid]-10,15,20-tris[3,5-di-tert-butylphenyl]-21H,23H-porphyrin (Ar-H2P-COOH), 5-[4-benzoic acid]-10,20-tris[3,5-di-tert-butylphenyl]-21H,23H-porphyrin (H-H2P-COOH), and 5,10,15,20-tetra[4-benzoic acid]-21H,23H-porphyrin (H2P-4COOH). The porphyrin-modified TiO2 nanoparticles were deposited on nanostructured OTE/SnO2 electrode together with nanoclusters of fullerene (C60) in acetonitrile-toluene (3/1, v/v) using an electrophoretic deposition technique to afford the porphyrin-modified TiO2 composite electrode denoted as OTE/SnO2/(porphyrin-modified TiO2 nanoparticle+C60)n. The porphyrin-modified TiO2 composite electrodes have efficient light absorbing properties in the visible region, exhibiting the photoactive response under visible light excitation using redox couple. The incident photon-to-photocurrent efficiency (IPCE) values of supramolecular nanostructured electrodes of porphyrin-modified TiO2 nanoparticles with fullerene [OTE/SnO2/(Ar-H2P-COO-TiO2+C60)n, OTE/SnO2/(H-H2P-COO-TiO2+C60)n, and OTE/SnO2/(H2P-4COO-TiO2+C60)n] are much larger than those of the reference systems of porphyrin-modified TiO2 nanoparticles without C60 [OTE/SnO2/(Ar-H2P-COO-TiO2)n, OTE/SnO2/(H-H2P-COO-TiO2)n, and OTE/SnO2/(H2P-4COO-TiO2)n]. In particular, the maximum IPCE value (41%) is obtained for OTE/SnO2/(H-H2P-COO-TiO2+C60)n under the bias potential of 0.2 V versus SCE. This indicates that the formation of supramolecular complexes between porphyrins and fullerene on TiO2 nanoparticles plays an important role in improvement of the light energy conversion properties. 相似文献
18.
Susana Rincón Jesús Sandoval-Ramírez Ma. Antonieta Fernández Rosa Santillan 《Tetrahedron》2006,62(11):2594-2602
The new (22R,23S,25R)-3β,16β,26-triacetoxy-cholest-5-ene-22,23-diol (11a) was synthesized from diosgenin (3) through a synthetic route based on chemoselective RuO4 oxidation of (25R)-3β,16β-diacetoxy-23-ethyl-231,26-epoxycholesta-5,23(231)-dien-22-one (9) that afforded (20S,25R)-3β,16β,26-triacetoxycholest-5-ene-22,23-dione (10) which was stereoselectively reduced using NaBH4. Compound 9 was obtained from the known isomeric 22,26-epoxycholest-5-ene steroidal skeleton 8b by treatment with p-TsOH in toluene, amberlyst-15 or directly from diosgenin by treatment with BF3·OEt2/Ac2O. Chemoselective reduction of the 23-keto group of 10, was attained using NaBH4/ZnCl2 at −70 °C to give 23S-14. The NMR spectra of all compounds were unambiguously assigned based on one and two dimensional experiments and the C-22 and C-23 stereochemistry in the diacetate derivative 11b, as well as the structure of epoxycholestene 9 were further established by X-ray diffraction analyses. The new route for the functionalization of the side chain of diosgenin can find application in the synthesis of norbrassinosteroid analogues. 相似文献
19.
John R Williams Deping ChaiJames D Bloxton II Hua GongWilliam R Solvibile 《Tetrahedron》2003,59(17):3183-3188
The aglycone of 26-O-deacetyl pavoninin-5, (25R)-cholest-5-en-3β,15α,26-triol, 5a, was synthesized in 10 steps in 17% overall yield from diosgenin, 3. Removing mercury from the Clemmensen reduction of diosgenin 3, gave a higher yield of (25R)-cholest-5-en-3β,16β,26-triol, 4, by a method, that is also more environmentally friendly. Attempted methods for the transposition of the C-16β hydroxyl to the 15α position are described. A successful method for this transposition via the 15α-hydroxy-16-ketone, 13, using the Barton deoxygenation reaction on the 16-alcohol, 15, is reported. 相似文献
20.
Tushar Gosavi 《Journal of organometallic chemistry》2005,690(13):3229-3236
The dinuclear platina-β-diketone [Pt2{(COMe)2H}2(μ-Cl)2] (1) was found to react with 2-(ROCH2)C5H4N (R = Me, 2a; H, 2b) yielding a cationic mononuclear platina-β-diketone [Pt{(COMe)2H}{2-(MeOCH2)C5H4N}]Cl (3) and an acetyl(chloro)platinum(II) complex [Pt(COMe)Cl{2-(HOCH2)C5H4N}] (4), respectively. The reaction of 1 with 8-(methylthio)quinoline (5) resulted in the formation of [Pt(COMe)Cl{8-(MeS)C9H6N}] (6). The identities of all complexes were established by microanalysis, 1H, and 13C NMR spectroscopy. Single-crystal X-ray diffraction analysis showed 6 to be square-planar platinum(II) complex with N and C atoms as well as Cl and S atoms in mutually trans positions (configuration index: SP-4-2). In accordance with this, quantum chemical calculations on the DFT level of theory revealed a higher stability of complex 6 having a SP-4-2 configuration vs. the analogous complex in SP-4-3 configuration. The distinctly different reactivity of 1 with 2a on the one hand and with 2b and 5 on the other is discussed in terms of the HSAB concept and a deprotonation/reprotonation reaction. 相似文献