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Steroidal plant growth hormone intermediates, I (R = H, Ac; R1 = MeC:CHMe, MeCHCOMe, MeCHQ, MeCHQ1) were prepared from hydrodeoxycholic acid (I, R = H, R1 = MeCHCH2CH2CO2H). 相似文献
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本文报道以3α-羟基-6-羰基-5α-胆烷酸甲酯(3)为原料经六步反应合成了油菜甾醇类似物25,26,27-三失碳-B-高-7-氧-6-酮-5α-胆甾-3α,24-二醇(9a).总产率14%.9a的促进植物生长作用是24-表油菜甾醇内酯的60%. 相似文献
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The discovery of the antibiotic fusidic acid from Fusidium coccineum in 19621 provided a valuable new medicinal agent, highly active against staphylococcal infections. Though various modifications of the tetracyclic structure (I) have so far failed to furnish derivatives with enhanced antibiotic activity2, no analogs of different skeletal configuration have yet been prepared for assessing the significance of the unique stereochemistry of the fusidane framework. For this purpose it would be desirable to have an effective method of attaching the fusidic acid sidechain to the 17-keto group of various steroids or to other ketones. 相似文献
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A Wittig reaction employing the ylide generated from isopropyl triphenylphosphonium bromide with THP-protected aldol intermediate 8 constitutes the key step in a regiospecific synthesis of olefin 1 in the total synthesis of zoapatanol analogue 2a. 相似文献
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Christos Tsiamantas Sunbum Kwon Joseph M. Rogers Cline Douat Ivan Huc Hiroaki Suga 《Angewandte Chemie (International ed. in English)》2020,59(12):4860-4864
Derivatives of 4‐aminomethyl‐l ‐phenylalanine with aromatic oligoamide foldamers as sidechain appendages were successfully charged on tRNA by means of flexizymes. Their subsequent incorporation both at the C‐terminus of, and within, peptide sequences by the ribosome, was demonstrated. These results expand the registry of chemical structures tolerated by the ribosome to sidechains significantly larger and more structurally defined than previously demonstrated. 相似文献
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Here we report the chemoenzymatic synthesis of Ro 25-8210 (1) and Ro 25-6630 (2) by using microbial reduction of a-chloromethyl ketone 4 mediated with baker's yeast and Geotrichum sp. to afford the optically active (R) and (S)-α-chlorohydrin 8 respectively as the key step. 相似文献
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《Helvetica chimica acta》2017,100(3)
Cell‐penetrating poly(disulfide)s (CPD s) have been introduced recently to explore new ways to enter into cells. In this report, we disclose a general method to covalently modify the sidechains of CPD s. Compatibility of copper‐catalyzed alkyne‐azide cycloaddition (CuAAC ) with the addition of either strained cyclic disulfides of varied ring tension or increasing numbers of guanidinium and phosphonium cations is demonstrated. Reloading CPD s with disulfide ring tension results in an at least 20‐fold increase in activity with preserved sensitivity toward inhibition with the Ellman 's reagent. The cumulation of permanent positive charges by sidechain engineering affords Ellman‐insensitive CPD s with similarly increased activity. Co‐localization experiments indicate that the CPD s reach endosomes, cytosol and nucleus, depending on their nature and their concentration. Supported by pertinent controls, these trends confirm that CPD s operate with combination of counterion‐ and thiol‐mediated uptake, and that the balance between the two can be rationally controlled. For the most active CPD s, uptake can be observed at substrate (fluorophore) concentrations as low as 5 nm . 相似文献
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Abstract Sidechain liquid-crystalline polymers were prepared by the derivatization of three poly(4-hydroxystyrene) fractions of different molecular weights (Mw = 1.0 × 104, 2.2 × 104 and 3.0 × 104). 4-Cyanoazobenzene and 4-cyanobiphenyl were incorporated as mesogenic groups with ether-linked methylene spacers of varying length. The polymers all exhibited a smectic A phase, with the exception of the propyl member of the cyanobiphenyl series for which no liquid-crystalline behavior was observed. For short spacers the thermal properties were insensitive to molecular weight changes in the backbone, whereas small but consistent differences in the transition temperatures and entropies were observed as the number of methylene groups in the spacer increased. 相似文献
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Qian LIU Gang FANG Li Ping WU Jian Mei CUI Xiao Tian LIANG Song WU Institute of Materia Medica Peking Union Medical College & Chinese Academy of Medical Sciences Beijing 《中国化学快报》2004,15(12)
A stereoselective and economic synthesis of the carbapenem sidechain (2S, 4S)-4-ace-tylsulphanyl-2-[(S)1-phenylethyl-carbamoyl] pyrrolidine-1-carboxylic acid 4-nitrobenzylester was developed. Due to the effect of spatial hindrance, only the (2S,4S) diastereomer 3 wasobtained by coupling 1 and the inexpensive racemic 2 catalyzed by EEDQ. 相似文献