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Total Synthesis of Some Important Natural Products from Brazilian Flora
Published in Luzia Valentina Modolo, Mary Ann Foglio, Brazilian Medicinal Plants, 2019
Leonardo da Silva Neto, Breno Germano de Freitas Oliveira, Wellington Alves de Barros, Rosemeire Brondi Alves, Adão Aparecido Sabino, Ângelo de Fátima
In 1993, Wang et al. described the stereoselective total synthesis of 7β-acetoxyvouacapane (38; Figure 12.12) in nine steps and an overall yield of approximately 18%. 7β-Acetoxyvouacapane is a tetracyclic furano diterpene isolated from plant species of the genus Pterodon, such as Pterodon apparicioi (Leguminosae; sucupira), a plant species from the banks of the Rio Cipó, state of Minas Gerais, Brazil (Fascio et al., 1976; Hansen et al., 2010). The key feature of Wang and coworkers' synthetic approach to 38 is access to the intermediary 39 using the stereoselective reductive hydrolysis of a tosylhydrazone 40. This reduction step does not work when traditional methods are used (LiAlH4/THF; Li(t-BuO)3AlH/THF; NaBH4/MeOH; Raney nickel/MeOH) because of steric hindrance of the 7-carbonyl group due to the 14α-methyl group (Figure 12.12) (Wang et al., 1993). The main disadvantage of the synthesis route for 7β-acetoxyvouacapane proposed by Wang and coworkers is that the furano diterpene is obtained in racemic form.
Barbiturates And Minor Tranquilizers
Published in S.J. Mulé, Henry Brill, Chemical and Biological Aspects of Drug Dependence, 2019
There are approximately four methods that have been employed for the synthesis of benzo-diazepin-2-ones, which are schematically presented in Figure 10. According to the first procedure, 2-amino-1, 4-benzodiazepine-4-oxide derivatives may be reacted with a weak acid to yield b e nzodiazepin-2-one-4-oxides.63 Deoxygenation of this product by catalytic hydrogenation over Raney nickel gives the corresponding benzo-diazepin-2-one.63 In the second method, amino-benzophenone is treated with a glycine ester to benzodiazepin-2-one directly.64 The most versatile procedure is method 3, because it affords higher yields of product.64,65 Here, aminobenzophenone is reacted with a haloacetyl compound to give haloacetamide, which on treatment with ammonia results in the formation of aminoacetamide. This product readily cyclizes to form benzodiazepin-2-one. In the last schematic reaction, aminobezo-phenone is acylated with a protected amino acid derivative such as carbobenzoxyglycine, carbo-benzoxyglycylchloride, carbobenzoxyglycine anhydride, or phthalimidoacetyl chloride.66 The protecting group is then removed to give the aminoacetamide compound which cyclizes to benzodiazepin-2-one.66
Glycerine Analysis
Published in Eric Jungermann, Norman O.V. Sonntag, Glycerine, 2018
The BP “halogenated compound” test is similar in comparing turbidity of silver chloride with a reference solution. Their limits are also about 30 ppm. But the BP uses a different procedure for releasing chlorides from the sample. To 5 ml of glycerine, 1 ml of 21 M sodium hydroxide, 10 ml of water, and 50 mg of Raney nickel catalyst is added. This mixture is heated for 10 minutes on a water bath and filtered. This is washed with water until 215 ml of aqueous solution is obtained. A 5 ml aliquot of this is mixed with 4 ml of ethanol, 2.5 ml of water, 0.5 ml of nitric acid to acidify, and silver nitrate to precipitate the silver chloride.
Discovery of novel dual inhibitors of receptor tyrosine kinases EGFR and PDGFR-β related to anticancer drug resistance
Published in Journal of Enzyme Inhibition and Medicinal Chemistry, 2018
Tim Fischer, Abdulkarim Najjar, Frank Totzke, Christoph Schächtele, Wolfgang Sippl, Christoph Ritter, Andreas Hilgeroth
Commercial reagents were used without further purification. The 4-chloro pyrimidine 1b was prepared according to literature starting from the prepared 6-amino-2-mercatopyrimidine-4-ol given by the reaction of cyano acetic acid methyl ester and thiourea in sodium methanolate, a following thioether hydrolysis using raney nickel and a final 4-chlorination reaction using phosphorus oxychloride in DMF18. The 1H-NMR spectra (400 MHz) were measured using tetramethylsilane as internal standard. TLC was performed on E. Merck 5554 silica gel plates. The ESI spectra were recorded on a Finnigan LCQ Classic mass spectrometer. Elemental analysis indicated by the symbols of the elements was within ±0.4% of the theoretical values and was performed using a Leco CHNS-932 apparatus.
Asymmetric organocatalysis in drug discovery and development for active pharmaceutical ingredients
Published in Expert Opinion on Drug Discovery, 2023
In 2015, Bae and Song described the synthesis of this target using a cinchona-squaramide catalyst 17 (Figure 2, D) [41]. This was an excellent piece of work as the reaction was performed at the multi-gram scale in brine using the nitroalkene 16 and dimethyl malonate 18 at 0°C to afford the Michael adduct 19 (not isolated) with >95% conversion and 91% ee, which was converted to a lactam via a Raney Nickel hydrogenation of the nitro group followed by cyclization and hydrolysis of the lactam to the (S)-pregabalin target (95% yield and 91% ee).