共查询到20条相似文献,搜索用时 15 毫秒
1.
《Bioscience, biotechnology, and biochemistry》2013,77(12):3116-3121
Mutilin (4) and deoxy analogues 2 and 3 are biosynthetic precursors of pleuromutilin (1) in the later stage of biosynthesis. Precursors 2 and 3 are required for studies on the oxygenation steps in biosynthesis, and were synthesized from readily available 1 via 4 by deoxygenation of the hydroxy groups. Feeding experiments with the 2H-labeled precursors confirmed their microbial conversion into 1. 相似文献
2.
Zhang L Liu HL Yang GH Huang XR Li Y Sun YB Sun CC 《Journal of molecular modeling》2011,17(12):3173-3181
A detailed doublet potential energy surface for the reaction of CH with CH3CCH is investigated at the B3LYP/6-311G(d,p) and G3B3 (single-point) levels. Various possible reaction pathways are probed.
It is shown that the reaction is initiated by the addition of CH to the terminal C atom of CH3CCH, forming CH3CCHCH 1 (1a,1b). Starting from 1 (1a,1b), the most feasible pathway is the ring closure of 1a to CH3–cCCHCH 2 followed by dissociation to P
3
(CH3–cCCCH+H), or a 2,3 H shift in 1a to form CH3CHCCH 3 followed by C–H bond cleavage to form P
5
(CH2CHCCH+H), or a 1,2 H-shift in 1 (1a, 1b) to form CH3CCCH2
4 followed by C–H bond fission to form P
6
(CH2CCCH2+H). Much less competitively, 1 (1a,1b) can undergo 3,4 H shift to form CH2CHCHCH 5. Subsequently, 5 can undergo either C–H bond cleavage to form P
5
(CH2CHCCH+H) or C–C bond cleavage to generate P
7
(C2H2+C2H3). Our calculated results may represent the first mechanistic study of the CH + CH3CCH reaction, and may thus lead to a deeper understanding of the title reaction. 相似文献
3.
Yoshiko Sato Kenji Ueyama Tokumi Maruyama Douglas D. Richman 《Nucleosides, nucleotides & nucleic acids》2013,32(1-3):109-119
Abstract Treatment of the 2,3-di-O-benzoate 1 with sodium boronhydride mainly afforded the 3-O-benzoate 2 accompanied with isomers 3a,b and fully deprotected product 4. Compound 2 was converted to 5, from which 8 was obtained. The 1-cyclobutanols 8 and 5 were successfully condensed with 6-chloropurine by Mitsunobu reaction to give 9 and 11, respectively. After partial deprotection, the cyclobutyl nucleosides 10 and 15 were subjected to fluorination using DAST to afford the fluoromethyl analogs 12 and 16 from which target compounds 14 and 17 were obtained in good yields, respectively. 相似文献
4.
【目的】研究一株西北太平洋深海沉积物来源真菌Aspergillus jensenii LW128的次级代谢产物及其抗菌活性。【方法】利用硅胶柱色谱(silica gel column chromatography)、凝胶柱色谱(Sephadex LH-20 column chromatography)和反相高效液相色谱(reversed-phase high-performance liquid chromatography, RP-HPLC)等方法对菌株的发酵粗提物进行分离纯化得到单体化合物;将核磁共振波谱(nuclear magnetic resonance, NMR)、质谱(mass spectrometry, MS)数据与相关文献报道数据进行比对后确定化合物结构;采用肉汤微量稀释法测定化合物的抗菌活性。【结果】从海洋真菌Aspergillus jensenii LW128中分离并鉴定了10个已知化合物,分别为diorcinol D(1)、diorcinol K(2)、diorcinol I(3)、(+)-(7S)-7-O-methylsydonic acid (4)、(+)-s... 相似文献
5.
Tateki Hayashi Mitsuo Namiki Keiichi Tsuji 《Bioscience, biotechnology, and biochemistry》2013,77(9):1955-1960
During the formation of radical A (2) and its precursor (tris(2-deoxy-2-L-ascorbyl)amine, 1) by the reaction of dehydroascorbic acid (DHA) with amino acid, ascorbic acid (AsA) and the reduced red pigment (3) were newly identified, in addition to scorbamic acid (SCA) and the red pigment (4), as intermediate products. The addition of AsA to the DHA-amino acid reaction, as well as to the DHA-SCA reaction, greatly increased the formation of 3 and 1. The reaction of AsA with 4 gave rapidly 3, followed by the gradual production of 1. From these results, a reaction pathway is proposed that 3 formed by the reduction of 4 with AsA is a key intermediate and its condensation with DHA followed by reduction with AsA might produce 2 and 1. 相似文献
6.
7.
8.
苦槛蓝叶中的黄酮类化合物 总被引:2,自引:0,他引:2
为了解苦槛蓝(Myoporum bontioides A.Gray)的化学成分,采用色谱分离技术从苦槛蓝叶片中分离得到11个黄酮类化合物。通过波谱分析,他们的结构分别鉴定为:桔皮素(1)、甜橙素(2)、5,4′-二羟基-6,7,8,3′-四甲氧基黄酮(3)、4′,5,7,8-四甲氧基黄酮(4)、去甲基川陈皮素(5)、5-羟基-6,7,3′,4′-四甲氧基黄酮(6)、3′,4′,5,6,7,8-六甲氧基黄酮(7)、二氢山柰酚(8)、木犀草素(9)、3′,4′,5,7-四羟基-3-甲氧基黄酮(10)和芹黄素(11)。除化合物9之外,其他化合物均为首次从苦槛蓝叶片中分离得到。孢子萌发法测定结果表明,化合物1,2,8和9对香蕉炭疽菌(Colletotrichum musae)具有较好的抑菌活性。这为苦槛蓝叶片中有效成分的利用提供了理论依据。 相似文献
9.
Claude Besuchet 《法国昆虫学会纪事》2013,49(1-2):155-172
The species belonging to Tychus rufus group are revised. Eleven species are recognized, described and illustrated and a key to their identification is provided. Nine taxa are new to science: Tychus carpathius n. sp. from Karpathos island (Greece); T. torticornis n. sp. from Lesbos Island (Greece); T. pisidicus n. sp. and T. inermis n. sp. from southwestern Turkey; T. antiocheus n. sp. and T. effeminatus n. sp. from southeastern Turkey; T. artvinensis n. sp. from northeastern Turkey, and T. sidonicus n. sp. and T. libanus n. sp. from Lebanon. 相似文献
10.
11.
《Bioscience, biotechnology, and biochemistry》2013,77(5):1230-1235
The filamentous fungus, Lambertella corni-maris (L. corni-maris), a mycoparasite on Monilinia fructigena, produces the antibiotics, lambertellols A (1), B (2), and lambertellin (3), in a substantial amounts under acidic conditions, whereas these antibiotics were hardly detected when the fungus was cultured on a potato-sucrose (PS) medium without added acids. Our investigations also revealed that the host, M. fructigena, changed its surroundings into acidic conditions, suggesting that the acidic conditions acted as kairomones that stimulated the production of 1–3. 相似文献
12.
13.
Summary InE. coli, sulfanilic acid, sulfanilamide, sulfapyridine, sulfapyrimidine and sulfathiazol are antagonized by the same series of non competitive antagonists,viz., methionine, xanthine, serine, thymine and valine. This seems to indicate that the biosynthesis of these substances is successively inhibited by increasing concentrations of these sulfadrugs; the synthesis of methionine being inhibited first, that of valine only by excessive concentrations. Though the absolute concentrations vary with the drug the relative sensitivity of the five enzyme systems are very much the same. This again shows that the intrinsic toxicity of the sulfadrugs is the same.I: Ann. de l'Inst. Pasteur62, 616, 1939. II: Antonie van Leeuwenhoek7, 25, 1941. III: Ibid.7, 77, 1941. IV: Ibid7, 153, 1941. V: Ibid.7, 161, 1941. VI: Ibid.8, 10, 1942. VII: Ibid.8, 86, 1942. VIII: Ibid.8, 139, 1942. IX: Ibid.9, 115, 1943. X: Ibid.10, 1, 1944–1945. XI: Arch. of Biochemistry18. 97, 1948. 相似文献
14.
Summary Cefotiam (7) and cefotaxime (8) are obtained by penicillin acylase hydrolysis of (5) and (6), prepared, in turn, by chemical condensation of 7-DIMAT (3) and 7-ACA (4), respectively, with N-phenacetyl-2-aminothiazol-4-yl acetic acids (1) and (2). 相似文献
15.
The three oligosaccharide octyl-S-glycosides Man-α1,6-Man-α1,4-GlcNH2-α1,S-Octyl (19), Man-α1,6-(Gal-α1,3)Man-α1,4-GlcNH2-α1,S-Octyl (27) and Man-α1,2-Man-α1,6-(Gal-α1,3)Man-α1,4-GlcNH2-α1,S-Octyl (37), related to the GPI anchor of Trypanosoma brucei were prepared by a stepwise and block-wise approach from octyl 2-azido-2-deoxy-3,6-di-O-benzyl-1-thio-α-d-glucopyranoside (8) and octyl 2-O-benzoyl-4,6-O-(1,1,3,3-tetraisopropyl-1,3-disiloxane-1,3-diyl)-1-thio-α-d-mannopyransoside (9). Glucosamine derivative 8 was obtained from 1,3,4,6-tetra-O-acetyl-2-azido-2-desoxy-β-d-glucopyranose (1) in five steps. Mannoside 9 was converted into the corresponding imidate 12 and coupled with 8 to give disaccharide octyl-S-glycoside 13 which was further mannosylated to afford trisaccharide 19 upon deprotection. Likewise, mannoside 9 was galactosylated, converted into the corresponding imidate and coupled with 8 to give trisaccharide 25. Mannosylation of the latter afforded tetrasaccharide 27 upon deprotection. Condensation of 25 with disaccharide imidate 35 gave, upon deprotection of the intermediates, the corresponding pentasaccharide octyl-S-glycoside 37. Saccharides 19, 27 and 37 are suitable substrates for studying the enzymatic glycosylation pattern of the GPI anchor of T. brucei. 相似文献
16.
AbstractThe developmental gene expression, morphogenesis, and population variation in mammalian molar teeth has become increasingly well understood, providing a model system for synthesizing evolution and developmental genetics. In this study, we estimated additive genetic covariances in molar shape (G) using parent-offspring regression in Cryptotis parva, the Least Shrew. We found that crown shape had an overall h2 value of 0.34 (±0.08), with higher heritabilities in molar cusps than notches. We compared the genetic covariances to phenotypic (P) and environmental (E) covariances, and to the covariances in crown features expected from the enamel knot developmental cascade (D). We found that G and D were not strongly correlated and that major axes of G (evolutionary lines of least resistance) are better predictors of evolutionary divergences in soricines than is D. We conclude that the enamel knot cascade does impose constraints on the evolution of molar shape, but that it is so permissive that the divergences among soricines (whose last common ancestor lived about 14 million years ago) do not fully explore its confines. Over tens of millions of years, G will be a better predictor of the major axes of evolution in molar shape than D. 相似文献
17.
18.
19.
为了解喙果皂帽花(Dasymaschalon rostratum)根的化学成分,采用多种色谱技术从其根的乙醇提取物中分离得到8个化合物。通过波谱数据分析,分别鉴定为:花旗松素(1)、(+)-儿茶素(2)、毛蕊异黄酮(3)、(-)-丁香树脂酚(4)、(-)-皮树脂醇(5)、lirioresinol A(6)、N-反式肉桂酸酰对羟基苯乙胺(7)和羟基酪醇(8)。所有化合物均为首次从该植物中获得。化合物1~8均无明显抗菌活性。 相似文献
20.
《Journal of enzyme inhibition and medicinal chemistry》2013,28(4):564-568
AbstractSome 4-piperidinol derivatives were synthesized and their cytotoxicity was tested against human hepatoma (Huh7) and breast cancer (T47D) cells. Aryl part was changed as phenyl in 2a, 4-methylphenyl in 2b, 4-methoxyphenyl in 2c, 4-chlorophenyl in 2d, 4-fluorophenyl in 2e, 4-bromophenyl in 2f, 4-nitrophenyl in 2g and 2-thienyl in 3. Compounds were synthesized and reported for the first time by this study except 2a and 2d. Chemical structures were confirmed by 1H NMR, 13C NMR, IR, MS and elemental analyses. Compounds 2a (3.1 times), 2c (3.8 times), 2f (4.6 times), 2g (1.3 times) and 3 (3.2 times) had 1.3–4.6 times higher cytotoxic potency than the reference compound 5-FU against Huh7 cell line while all the compounds synthesized had shown lower activities against T47D cell line than 5-FU. In the light of these results, compounds 2a, 2c, 2f, 2g and 3 may serve as model compounds for further studies. 相似文献