Practical synthesis of the new carbapenem antibiotic ertapenem sodium

[reaction: see text] A practical synthesis for the large-scale production of the new carbapenem antibiotic, [4R,5S,6S]-3-[[(3S,5S)-5-[[(3-Carboxyphenyl)amino]carbonyl]-3-pyrrolidinyl]thio]-6-[(1R)-1-hydroxyethyl]-4-methyl-7-oxo-1-azabicyclo[3.2.0]hept-2-ene-2-carboxylic acid monosodium salt (ertapenem sodium, 1), has been developed. The synthesis features the novel use of 1,1,3,3-tetramethylguanidine as base for the low-temperature reaction of a thiol, derived from trans-4-hydroxy-L-proline, with the carbapenem nucleus activated as the enol phosphate. Hydrogenolysis of a p-nitrobenzyl ester is effected using a palladium on carbon catalyst to give an overall yield for the two steps of 90%. The use of bicarbonate in the hydrogenolysis was key in providing protection of the pyrrolidine amine as the sodium carbamate improving both the performance of the reaction and the stability of the product. This discovery made processing at manufacturing scale possible. Experimental evidence for the formation of the sodium carbamate is provided. A remarkably expedient process for the simultaneous purification and concentration of the aqueous product stream relies on ion-pairing extraction for the removal of the water-soluble 1,1,3,3-tetramethylguanidine. Crystallization then affords 59-64% overall yield of the monosodium salt form of the product.     

Diastereoselective synthesis of (2R,4R)-2-aryl-4-hydroxypyrrolidine: preparation of the side chain of novel carbapenem.

Improved synthesis of the trans-3,5-disubstituted pyrrolidin-3-ylthio side-chain of the novel carbapenem 1 was achieved via stereoselective reduction of the 1-aryl-1-butanone derivative 5 and successive intramolecular cyclization of the resulting chiral alcohol 6. The 1-aryl-1-butanone derivative 5 was obtained by a coupling reaction of protected 4-hydroxy-2-pyrrolidone with aryl-Grignard reagent.     

Efficient one-pot synthesis of ethyl 2-substitued-4-methylthiazole-5-carboxylates

A new and practical one-pot procedure for the synthesis of several 2-sustituted-4-methylthiazole-5-carboxylates from commercially available starting materials is described. Under mild reaction conditions, some of the products with alkyl group on the 2-amino group or with various groups on 2-substituted phenyl ring were obtained in good yields from ethyl acetoacetate, N-bromosuccinimide, thiourea, or its N-substituted derivatives in an efficient way instead of the traditional two-step reaction.     

Synthesis of a new carbapenem with a 6-methyl hydroxyacetate side chain

The synthesis of the 2-(4-pyridinylthio)-carbapen-2-em-3-carboxylic acid 1b, bearing a 6-methyl hydroxyacetate side chain, is described.     

Efficient one-pot synthesis of 2-hydroxyethyl per-O-acetyl glycosides

A class of stereo-isomerically-pure alkanediol monoglycosides, 2-hydroxyethyl per-O-acetyl pyranosides (IIIa-IIIf), was conveniently prepared by a one-pot reaction of per-O-acetylated pyranoses (Ia-If) and 2-(tert-butyldimethylsilyloxy)ethanol (II) with catalysis by BF₃·OEt₂. The α-(IIIa) or β-linked glycosides (IIIb-IIIf) with 1,2-trans-configuration were obtained from glycosyl donors with participation of the neighbouring 2-O-acetyl group. BF₃·OEt₂, along with hydrogen fluoride released from BF₃·OEt₂ under the experimental conditions used, facilitates the subsequent de-protection of siloxane to successfully afford 2-hydroxyethyl per-O-acetyl-pyranosides.     

Efficient one-pot synthesis of substituted 2-amino-1,3,4-oxadiazoles

A convenient one-pot method for the preparation of substituted 2-amino-1,3,4-oxadiazoles has been developed. The method is a significant improvement over previously reported syntheses. Reaction of carboxylic acids with thiosemicarbazides afforded the corresponding oxadiazoles in moderate to good yields. In general, the products precipitated from the reaction mixture, and were collected by filtration. In most of the cases, no chromatographic separations were required. To explore the scope and limitations of this reaction, various aliphatic, aromatic, and heteroaromatic carboxylic acids were reacted with different substituted thiosemicarbazides. The influence of R¹ and R² substituents on the reaction yield and additional results demonstrating the versatility of this method are presented.     

Efficient one-pot synthesis of glycosyl disulfides

Methodology for the efficient and facile synthesis of glycosyl disulfides is reported. A one-pot procedure employing mild conditions using diethyl azodicarboxylate is described to synthesise a series of glycosyl disulfides in excellent yields.     

Efficient one-pot synthesis of substituted pyrazoles

An efficient, one-pot synthesis of substituted pyrazoles from enones, hydrazides, and halides was developed. In comparison with the classical Knorr pyrazole synthesis, this methodology gave a different type of product (R³≥R⁵). A range of substituted pyrazoles were prepared in good to high yields with complete regioselectivity.     

A short-step synthesis of orally active carbapenem antibiotic CS-834

An orally bioavailable carbapenem CS-834, which is a pivaloyloxymethyl (POM) ester-type prodrug and has (R)-5-oxopyrrolidin-3-ylthio moiety at the C-2 position of the 1 beta-methylcarbapenem skeleton, is currently under clinical trial. We accomplished a short-step synthesis of CS-834 by using phosphorus ylide from the intramolecular Wittig-type reaction in the key step for cyclization to the bicyclic carbapenem system. The POM ester group was found to be suitable for the cyclization conditions.     

Efficient one-pot synthesis of propargylamines using zinc dust

The one-pot synthesis of propargylamines is achieved efficiently via a three component coupling of various aldehydes, alkynes and amines using zinc dust under mild reaction conditions and in the absence of a co-catalyst. Zinc dust was recovered quantitatively by simple centrifugation and reused.     

Efficient one-pot, two-step, microwave-assisted procedure for the synthesis of polysubstituted 2-aminoimidazoles

A microwave-assisted, one-pot, two-step protocol was developed for the construction of polysubstituted 2-aminoimidazoles. This process involves the sequential formation of imidazo[1,2-a]pyrimidinium salts from readily available 2-aminopyrimidines and alpha-bromocarbonyl compounds, followed by opening of the pyrimidine ring with hydrazine. [reaction: see text]     

Efficient one-pot synthesis of n-butyl levulinate from carbohydrates catalyzed by Fe_2(SO_4)_3

Butyl levulinate(BL) is a promising new candidate as diesel fuel and fuel additive. In this study, an efficient process for a one-pot synthesis of BL from biomass-derived carbohydrates in butanol medium with the catalysis of metal sulfates was developed. The catalytic activity of a series of metal sulfates for the synthesis of BL from fructose was investigated. Among various metal sulfates, ferric sulfate Fe_2(SO_4)_3 was found to be the most efficient catalyst, which gave a remarkably high BL yield of 62.8 mol% under the conditions of 463 K, 3 h, a catalyst dosage of 5.0 g/L, and fructose concentration of 25 g/L. Different carbohydrates including glucose, cellulose, inulin and sucrose were also used for one-pot synthesis of BL with the catalysis of Fe_2(SO_4)_3, showing the yields of 39.6, 30.5, 56.6 and 50.1 mol%, respectively. In addition,the recycling and reuse of Fe_2(SO_4)_3 was studied by characterizing them using powder X-ray diffraction(XRD), scanning electron microscope(SEM), X-ray photoelectron spectroscopy(XPS). A plausible reaction pathway for the one-pot synthesis of BL from fructose was proposed. This study provides a facile and feasible way for the synthesis of BL from biomass.     

Efficient atom economical one-pot multicomponent synthesis of densely functionalized 4H-chromene derivatives

A sequential one-pot, atom economical three component reaction yielding medicinally promising ethyl 2-amino-3-cyano-4-(2-ethoxy-2-oxoethyl)-5-oxo-5,6,7,8-tetrahydro-4H-chromene-4-carboxylate derivatives (4a-f) through a tandem Michael addition-cyclization reaction starting with structurally diverse cyclohexane-1,3-dione, diethyl acetylene dicarboxylate, and malononitrile has been carried out in different organic bases under solvent free condition for the optimization of maximum yield. All the formed 4H-chromenes were characterized by spectral and X-ray methods.     

微波促进下4-乙炔基苯磺酰胺的“一锅法”合成

以3-(4-氯磺酰苯基)-2,3-二溴丙酸和氨水（2.2 eq）为原料,以 DMF为溶剂,经微波辐射25 s,磺酰胺化和脱溴脱羧反应可同步进行,立体选择性地合成中间体(Z)-4-(2-溴乙烯基)苯磺酰胺;该中间体不需分离,直接向反应体系中加入1,8-二氮杂环[5,4,0]十一烯-7 (DBU,2eq),再微波辐射1 min,“一锅法”得到4-乙炔基苯磺酰胺,并通过1H NMR和13C NMR和IR进行了表征,收率达70%。     

A new and efficient one-pot procedure for the synthesis of 2-styrylquinolines

A one-pot combination of a modified Friedländer annulation and a Knoevenagel condensation provides 2-styrylquinolines in good to excellent yields. A variety of substrates are reacted in one-pot in the presence of 1-methylimidazolium trifluoroacetate ([Hmim]TFA).     

Efficient one-pot synthesis of anti-HIV and anti-tumour β-carbolines

Thermal electrocyclisation of the azahexatriene system has been used as a key step for the synthesis of anti-HIV and anti-tumour compounds, harman, derivatives of harman and 1-aryl-β-carbolines. A one-pot reaction sequence was used to furnish these compounds in good yield.