共查询到20条相似文献,搜索用时 93 毫秒
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近年来,有机小分子催化的串联反应已成为众多有机化学家们的研究热点,是合成手性化合物的有效方法。在众多不同催化体系中,手性叔胺催化的不对称串联反应得到了空前的发展。氧化吲哚螺环骨架是很多具有药理活性分子普遍存在的结构形式,含有该骨架的化合物是众多药物及有机化学家们的目标产物,不对称催化串联反应是合成氧化吲哚螺环化合物的重要理论基础和有力学术支撑。本文对近四年手性叔胺催化的不对称串联反应构建氧化吲哚螺环化合物的研究进行介绍。 相似文献
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《高校化学工程学报》2021,35(5)
轴手性化合物是许多天然产物、药物中间体、手性配体的核心骨架,在手性化合物中占有重要地位。与金属催化剂催化的不对称化学偶联反应等化学方法相比,生物催化方法具有选择性高、反应条件温和、环保等优势。随着酶的改造等关键技术的快速发展,酶催化轴手性化合物的合成成为新的研究热点与难点。从动力学拆分(kinetic resolution,KR)、动态动力学拆分(dynamic kinetic resolution,DKR)以及去对称化(desymmetrization)等不对称合成方法入手,综述了生物催化轴手性化合物的合成领域的主要研究成就,并阐述了此方向的发展前景、应用及存在的问题。 相似文献
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不对称aza-Henry反应是重要的碳碳键形成反应,手性产物β-硝基胺是许多药物和天然产物的关键中间体,利用该反应构建手性化合物已有广泛报道,其中有机催化不对称aza-Henry反应已成为不对称催化领域的重要研究对象。催化不对称aza-Henry反应的有机小分子催化剂主要有硫脲类催化剂和相转移催化剂,其中硫脲类催化剂占主要部分,其次还有方酰胺类、胍酰胺类以及脲类等催化剂。对近5年有机催化不对称aza-Henry反应的发展现状进行概述并作出总结与展望,以期为今后有机催化不对称合成研究提供参考。 相似文献
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X. D. Liu 《Drying Technology》1999,17(9):1813-1826
An attempt was made to determine the kinetic model, which describes the degradation of activity and viability during thermal drying of baker's yeast. The pellels of baker's yeast were dried under a variety of conditions using a laboratory scale VFB dryer to generate a broad database. The data used in determining the parameters for the kinetic model, such as the average moisture content, temperature as well as the relative activity and viability of baker's yeast were measured under dynamic procedure. The extensive data from the experiments under variety conditions enable the model to predict the quality retention of baker's yeast in a rather wide range during thermal drying, The interpretation procedure of raw data was described in detail. 相似文献
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报道了用4 氯 乙酰乙酸乙酯为原料,以面包酵母为还原剂,选择性合成(s) 4 氯 3 羟基丁酸乙酯。分别考察了能源供体、蔗糖浓度、反应温度、底物加量和压榨酵母用量等因素对产物收率和对映体过量值的影响。结果表明,4 氯 乙酰乙酸乙酯不对称生物还原反应的适宜条件为:能源供体40.0g/L蔗糖,反应温度36.5℃,压榨酵母50.0g/L,底物加量12.0g/L,pH为7 0。反应收率可达60 5%,ee收率为98 5%。 相似文献
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M. Dicke J. C. Van Lenteren G. J. F. Boskamp E. van Dongen-van Leeuwen 《Journal of chemical ecology》1984,10(5):695-712
Chemical stimuli play an important role in the process of searching for a host habitat by parasitic wasps. Volatile compounds originating from host habitats and/or hosts are the cues that enable such a location.Leptopilina heterotoma, a larval parasite ofDrosophila, is attracted to the food of its host, baker's yeast. Analysis of the fermentation products of baker's yeast, using a mass spectrometer, and olfactometer studies indicate that three fermentation products of this yeast, the main component of the host habitat in our laboratory, attractL. heterotoma: ethanol (5%), ethyl acetate (10–2, 10–3%), and acetaldehyde (1%). A combination of these three compounds, however, cannot compete with baker's yeast in attracting the parasites. Thus other factors, such as different compounds, concentrations, and/or combinations, also, play a role and remain to be tested.Leptopilina heterotoma does not use host-related olfactory cues in long-distance habitat location as it cannot distinguish between host habitat and host habitat with hosts. 相似文献
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目的研究富GTF啤酒酵母制品对糖尿病大鼠空腹血糖和糖耐受量的影响。方法采用腹腔注射四氧嘧啶建立糖尿病大鼠模型,将模型大鼠随机分为3组,分别每天服用普通面包酵母0.1g、富GTF啤酒酵母干粉0.1g和富GTF啤酒酵母胶囊1粒,每天测空腹血糖。30d后进行糖耐受量试验,测0、0.5和2h各时间点血糖。结果富GTF啤酒酵母胶囊和富GTF啤酒酵母干粉不降低正常大鼠血糖。服药30d后,富GTF啤酒酵母胶囊组糖尿病大鼠空腹血糖下降52.45%,富GTF啤酒酵母干粉组血糖下降32.34%,而面包酵母干粉无降糖作用。各样品组糖耐受量2h后均下降,富GTF啤酒酵母胶囊组血糖下降迅速。结论富GTF啤酒酵母胶囊降血糖效果显著,优于富GTF啤酒酵母干粉,并能显著改善糖尿病大鼠糖耐受量。 相似文献
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Adam S. Markowski 《Drying Technology》1993,11(2):369-387
An experimental study was conducted to apply the jet spouted bed (JSB) dryer with inert bodies for drying of fodder antibiotic; (zinc-salt bacitracin and tylosin) and baker's yeast which are extracted from fermentation broth. After establishing the drving properties of these products (e.g. sorption isotherm, water activity and thermostability), the influence of basic drying parameters (temperature of drying agent, bed loading, gas flow rate) on drying characteristics and quality of the products was determined. The results proved that a JSB dryer may be successfully applied to fodder antibiotics; especially to Zn-bacitracin; however, for a highly labile live organism like baker's yeast, this method cannot be used. The optimal parameters for drying of Zn-bacitracin have been presented. 相似文献
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Properly chosen additives (carriers) can protect the material or decrease water content in it. The papcr presents results of measurements of sorption isotherms of baker's yeast Saccharvmyces cerevisiae dried in an oven dryer and in a fluidized bed with and without carriers. The authors propose an original method for calculation of sorption isotherms for multicomponent mixtures containing yeast. Results of the calculations were compared with experimental data. 相似文献
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Ritsuo Nishida Dr. Yasumasa Kuwahara Hiroshi Fukami Shoziro Ishii 《Journal of chemical ecology》1979,5(2):289-297
The component of the sex pheromone of the German cockroach, 3, 11-dimethyl-2-nonacosanone (compound A), is a chiral compound. The chiral center at C-3 was assigned theS-configuration by ORD studies and PMR studies using a chiral shift reagent. 相似文献
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手性4-哌啶酮衍生物的合成 总被引:1,自引:0,他引:1
哌啶酮及其衍生物是一类非常重要的医药、农药和化工中间体。采用手性羟胺类化合物(手性试剂)与丙烯酸甲酯反应成功地合成了几个新的含羟基的手性N取代4-哌啶酮类化合物,采用核磁共振波谱对其结构进行了表征。 相似文献