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181.
2β,3α-Dihydroxyurs-12-en-28-oic acid(6) is a naturally occurring diastereoisomer of corosolic acid with glycogen phosphorylase inhibitory activity.A new strategy for the semi-synthesis of 6 was developed.Using the commercially available ursolic acid(1) as the starting materials,6 was synthesized through five facile reactions with a high stereoselectivity and an overall yield of 47.3%.The structure of 6 was confirmed by optical rotation.ESI-MS,1H NMR and 13C NMR data. 相似文献
182.
Paweł Punda 《合成通讯》2013,43(10):1362-1367
A one-pot synthesis for the preparation of N-alkenyl-malonamides and N-alkenyl-thiomalonamides was developed. 5-[Hydroxy/mercapto(aryl/alkylamino)methylene]-2,2-dimethyl-1,3-dioxane-4,6-dione act as a source of ketenes that react with the tautomeric form of alkyl-(2-phenyl-propylidene)-amines. A possible [2 + 2] or [4 + 2] cycloaddition product of ketene to imines was not observed. 相似文献
183.
A synthesis of N‐protected β‐aminomalonates starting from α‐amidosulfones under very mild and simple reaction conditions is described. Treatment of the sulfones with malonate esters in the presence of 2.5 equivalents of potassium carbonate affords the desired products in good yield. A variety of N‐Z and N‐Boc protected aliphatic and aromatic α‐aminosulfones and malonate esters have been successfully used as starting materials. Hydrolysis with concomitant decarboxylation of the N‐protected β‐aminomalonates provides a convenient access to racemic β‐amino acids. 相似文献
184.
A fatty epoxide (tetradecyl-oxirane) is reacted with diethyl acetamidomalonate in basic medium, with or without solvent under solid-liquid phase transfer catalysis with LiCl, or under microwave irradiation on supported reagents (KF/Al2O3/LiCl). The main product is a lactone which is formed after epoxide ring opening and subsequent cyclisation. We put here into evidence, for the first time, the conjugated advantages of “dry media” reactions, lithium salt effects and microwave irradiation. 相似文献
185.
The Knoevenagel condensation of Meldrum's acid with aromatic aldehydes proceeded efficiently in a reusable ionic liquid, ethylammonium nitrate, at room temperature in the absence of any catalyst with high yields. 相似文献
186.
Meldrum's acid (1) on bisacylation with succinyl chloride afforded a neutral diketo product (2); however, the dimer enolic products (3) with acidic nature resulted in glutaryl and adipyl dichlorides. Monoacylation of (1) with acetyl chloride gave acidic 5‐acetyl Meldrum's acid (4) in enol form. 相似文献
187.
Efficient syntheses of xanthenes have been described using a catalytic amount of perchloric acid in water. The high temperature and lengthy reaction time normally required for formation of xanthenes derivatives are not necessary when using a catalytic amount of perchloric acid. The method is relatively inexpensive, easily available, nonvolatile, nonexplosive, and thermally robust to catalyze the reaction at 80 °C by simple heating with good to excellent yields. The advantages of the reaction involve simple reaction protocol, simple workup, and improved synthesis in the presence of perchloric acid as catalyst. 相似文献
188.
2-Aminoarylketones undergo smooth condensation with α-methylene ketones in the presence of 10 mol% of poly(ethylene glycol) (PEG)–supported sulfonic acid under mild reaction conditions to afford the corresponding poly-substituted quinolines in excellent yields. The catalyst can be recovered by simple filtration and can be recycled in subsequent reactions. The method is simple, cost-effective, and environmentally benign. 相似文献
189.
A series of highly functionalized piperidine derivatives was synthesized through one-pot, five-component reaction of aldehydes, amines, and β-ketoesters. Silica sulfuric acid efficiently catalyzes the reaction to afford the corresponding piperidine derivatives in good yields. As a representative example, heating of 4-methylaninle, 4-fluorobezaldehyde, and methyl-acetoacetate in methanol in the presence of silica sulfuric acid furnished the corresponding ethyl 2,6-bis(4-fluorophenyl)-1-p-tolyl-4-(p-tolylamino)-1,2,5,6-tetrahydropyridine-3-carboxylate in excellent yield (85%). Most of the synthesized compounds were screened in vitro for their antibacterial and antifungal activities. Most of compounds showed significant antibacterial activity. 相似文献
190.
The preparation of 7-ethoxy-5-fluoroquinazolin-4-one, starting from 3,5-difluorophenol, is described. Further reaction with alkoxide then gives differentially substituted 5,7-dialkoxyquinazolin-4-ones. 相似文献