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首次将穿心莲内酯与2,3,4,6-四- O -乙酰基- β -D-溴化吡喃葡萄糖通过Koenigs-Knorr反应及二丁基氧化锡脱保护方法合成穿心莲内酯糖苷衍生物,所得糖苷结构经IR,NMR及高分辨质谱分析证实。实验结果表明:用二丁基氧化锡脱乙酰保护基的方法,反应条件比较温和,可以选择脱除糖元上的乙酰基,保留苷元乙酰基,且不影响分子中的酸碱敏感基团。 相似文献
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在固相多肽合成中,Dmab作为羧基保护基具有脱保护条件温和、步骤简便、选择性高的特点,但有时脱保护效率并不稳定.为此,基于Fmoc/t Bu/Dmab三维正交保护策略,利用固相多肽合成技术设计并合成了4个肽树脂,对固相多肽合成中Glu和Asp主链和侧链羧基的Dmab保护基脱除规律进行了研究.结果显示,树脂上α-ODmab的脱保护快速、完全,β-ODmab和γ-ODmab脱保护反应较慢,可以检测到相应的中间产物(4-氨基苄酯肽),推测脱保护效率由快到慢依次为α-ODmabβ-ODmabγ-ODmab.该结果表明Dmab作为α-COOH保护基具有较高的应用价值,但用于β-COOH和γ-COOH保护时,其脱保护条件尚不成熟. 相似文献
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脱二苯膦酰(Ph_2P(O))保护基/分子间炔烃偶联环化反应可一锅进行,高效形成环苯基六炔烃.与Haley等的脱硅基/Eglington偶联分步反应的制备方法相比,极性Ph_2P(O)保护基使产物与少量剩余原料具有不同极性而易分离,且本反应与产物Rf值相近的分子间偶联副产物量较少,使得产物易分离.且一锅反应可避免脱Ph_2P(O)的后处理,减少化合物损失,有效提高了环苯基六炔烃的产率.此外,本方法还具有中间体易制备、反应条件温和等优点. 相似文献
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壳聚糖超声可控降解及降解动力学研究 总被引:1,自引:0,他引:1
通过正交实验法考察了壳聚糖溶液浓度、反应温度、超声强度以及醋酸溶液浓度对超声降解反应的影响,确定了最佳反应条件,制备了一系列不同分子量的壳聚糖.研究了壳聚糖溶液浓度、反应温度以及壳聚糖原料分子参数与降解速率常数的关系.通过红外光谱、X-射线衍射和凝胶渗透色谱对降解产物进行了表征.结果表明,超声降解壳聚糖的最佳条件为10℃,壳聚糖溶液浓度2.5g/L.降解速率常数随壳聚糖溶液浓度和反应温度的降低而增大.高分子量和低脱乙酰度的壳聚糖原料有较高的降解速率和降解速率常数,壳聚糖原料的分子量对降解速率和降解速率常数的影响大于脱乙酰度对其的影响.超声波导致了壳聚糖分子量的降低和产物晶体结构的破坏,但没有改变产物的脱乙酰度和糖残基结构. 相似文献
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采用收敛法合成了3代内核为1,4,5,8-萘酰亚胺, 端基分别含8个和16个乙基的三嗪树枝状大分子, 产物经IR, 1H NMR, 13C NMR及元素分析表征. 实验结果表明, 该方法无需保护/脱保护, 反应条件温和, 收率非常高. 通过荧光光谱对其荧光特性进行了初步研究, 发现经过树枝状修饰后的产物具有更好的荧光性能, 且随着代数的增加, 树枝状产物的荧光强度不断增强. 相似文献
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羟丙基三甲基氯化铵壳聚糖制备的可控性研究 总被引:5,自引:0,他引:5
用壳聚糖与缩水甘油三甲基氯化铵反应制备羟丙基三甲基氯化铵壳聚糖,所得产物的结构受壳聚糖分子量和脱乙酰度、反应温度、反应时间、壳聚糖与缩水甘油三甲基氯化铵投料比的影响。实验结果表明:随着反应温度升高,羟丙基三甲基氯化铵壳聚糖的取代度增加,在70~80℃达最大;反应时间增加,取代度增加,产物分子量降低。缩水甘油三甲基氯化铵与壳聚糖比例达3:1前取代度随比例升高而增加。脱乙酰度和分子量越大的壳聚糖其季铵盐取代度越高。控制反应温度在30~90℃,反应时间3~10h,投抖比为1:1~4:1,可以得到取代度15%~909/6,分子量1万到100万的羟丙基三甲基氯化铵壳聚糖。 相似文献
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乙酰鸟氨酸脱乙酰酶固定化细胞拆分D,L-缬氨酸 总被引:3,自引:1,他引:3
报道了一种利用具有乙酰鸟氨酸脱乙酰酶活性的固定化细胞拆分D,L-缬氨酸的新方法. 该酶促反应最适条件: pH=6, 反应温度50 ℃, 底物N-乙酰-D,L-缬氨酸浓度200 mmol/L, 固定化细胞用量0.2 g/mL(或100 U/mL). 0.1 mmol/L CoCl2条件对该酶促反应有显著的激活作用. 在以上条件下反应2~3 h, 测得产物L-缬氨酸浓度95 mmol/L. 该固定化细胞连续10次使用, 平均转化率为90.8%(以N-乙酰-L-缬氨酸计), 显示出了良好的工业化应用前景. 相似文献
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Palladium-catalyzed microwave-assisted amination of 1-bromonaphthalenes and 5- and 8-bromoquinolines
[reaction: see text] 1-Aminonaphthalenes and 5- and 8-aminoquinolines were rapidly prepared from the respective aryl bromides in good yields by Pd-catalyzed aryl amination under microwave conditions. Consistent improvements in yields over those obtained under standard conditions were seen with quinoline substrates. In the cases where 5-bromo-8-cyanoquinoline was used as a substrate, no desired products were obtained under standard conditions with a number of different primary and secondary amines. However, microwave conditions provided the desired products in good to excellent yields. 相似文献
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The synthesis of various 1,4‐dihydropyridine and polyhydroquinoline derivatives was achieved in good to excellent yields using cadmium (II) nitrate as catalyst to promote the classical and modified Hantzsch conditions in good yields under mild conditions. 相似文献
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Feng Zhang Ya Zhuo Li Da Wei Gao Ji Kui Sun Yu Min Zhang 《中国化学快报》2007,18(7):791-794
A series of new diethers were obtained by alkylation of furoin under microwave irradiation (MWI) in phase transfer catalysis (PTC) conditions. The products of alkyl halides were synthesized in good yields (>75%) within a few minutes, and the products of dihalides were synthesized in fair yields (about 45%). The yields are dramatically improved compared to conventional heating under the same conditions, in spite of similar profiles of rising in temperature. 相似文献
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The treatment of amines with formic acid in the presence of ZnO under solvent-free conditions brings about highly and efficient N-formylation to give the corresponding formamides in excellent yields. The N-formylation reaction not only involves mild conditions, simple operation, and high yields but also high chemoselectivity. 相似文献
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Ethenylbenzothiazoles were synthesized by the Horner-Emmons reaction of benzothiazolylmethylphosphonate with aldehydes under phase transfer catalytic conditions in 60–71% yields. Not only aromatic but also aliphatic aldehydes gave the desired products under these mild conditions in 66–71% yields. 相似文献
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Polypropylene (PP) and Polyamide 6 (PA6) samples, with and without fire retardants (FR) (ammonium polyphosphate in PP, and a mixture of organic aluminium phosphinate and melamine polyphosphate (OP 1311) in PA 6) and nanofillers (NC) were burned under different fire conditions in order to compare their toxic product yields. Fire effluents (CO, smoke and hydrocarbons) were generated using a steady state tube furnace (BS 7900, ISO TS 19700) for the separate materials and fire retarded and nanocomposite modifications of these materials under flaming conditions. Under well-ventilated conditions yields of carbon monoxide (CO) for all PP samples are similar, whereas for PA6 samples much higher yields of CO for PA6 + FR and PA6 + NC are observed. The highest yields of CO occur for both pure polymers in under-ventilated fire conditions when fire retardant and nanoclay are combined together. For PP the smoke is fairly independent of fire condition, but the PP + FR + NC shows less agglomeration. For PA6 the sample containing OP 1311 shows consistently higher smoke yields. For hydrocarbon yields similar effects are observed for both PP and PA6 polymers; the highest yields are for PA6 + NC, except under-ventilated fires where PA6 + FR produce the most; for PA6 + FR + NC samples the lowest yields are observed, compared to either NC or FR formulations. 相似文献
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Epoxides react smoothly with tetraallyltin in the presence of 2 mol% of Bi(OTf)3 under mild reaction conditions to afford the corresponding homoallylic alcohols in excellent yields with high regioselectivity while aryl aziridines produce exclusively allyl amines in good yields under similar conditions. 相似文献
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B.V. Subba Reddy A. Siva KrishnaA.V. Ganesh G.G.K.S. Narayana Kumar 《Tetrahedron letters》2011,52(12):1359-1362
The three component, one-pot synthesis of α-aminophosphonates has been achieved using super magnetic nano iron oxide at 50 °C under solvent-free conditions in excellent yields. The major advantages of the present method are high yields, short reaction times, magnetically recyclable catalyst, and solvent-free reaction conditions. 相似文献
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Novel C6-phosphonated purine nucleosides were obtained in good to excellent isolated yields by the simple and catalyst-free SNAr-Arbuzov reaction of trialkyl phosphite with 6-choloropurine nucleosides, including a series of nonsugar carbon nucleosides. Shorter reaction times were needed, and substantially higher yields were obtained under microwave irradiation conditions compared with conventional heating conditions. 相似文献
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Santosh V. Goswami Prashant. B. Thorat Vijay N. Kadam Sachin A. Khiste Sudhakar R. Bhusare 《中国化学快报》2013,24(5):422-424
An efficient protocol was developed for the synthesis of 3-aminoalkylated indoles using 3-chlorophenylboronic acid as a catalyst under ambient temperature conditions. The three-component reaction of indoles, aromatic aldehydes and N-methyl aniline offered corresponding 3-aminoalkylated indoles in excellent yields. This protocol presents some remarkable features such as mild reaction conditions, simple workup procedure and excellent yields. 相似文献