The synthesis of fexofenadine

This work proposes a new simple route for fexofenadine synthesis with low cost and easily obtainable raw materials. We use benzene and methallyl as starting reactants, applying steps of Friedel–Crafts alkylation reaction, hydrolysis, oxidation, esterification reaction, and reduction reaction to obtain the intermediate product, followed by N-alkylation reaction to obtain 4-{1-hydroxy-4-[4-(hydroxydiphenyl)-piperidine]butyl}-α,α-dimethylbenzene acetate. Then, the final product fexofenadine is obtained upon hydrolysis. In the synthesis process, we constantly optimize the reaction conditions such as reaction time, reaction temperature, solvent selection, and other factors, thus improving the final yield of the target product fexofenadine to 33.51 %.     

Chichibabin pyridinium synthesis

Chichibabin pyridine synthesis involves the reaction of three aldehydes and ammonia to form 2,3,5-trisubstituted pyridines. This study examined the synthesis of tetrasubstituted pyridinium from aldehydes and an amine hydrochloride in the presence/absence of Pr(OTf)₃. Important insights into the reaction mechanisms of Chichibabin pyridinium synthesis were proposed through the investigation of reaction intermediates along with quantitative GC–MS analysis.     

Heterodiene synthesis

Both 1,4,-cycloaddition with the formation of a 1,4-dihydro-1,2,4-triazene derivative and electrophilic addition of acetyldicarboxylic acid ester to the secondary nitrogen atom occur during the reaction of acetylenedicarboxylic acid ester with 1,5-diphenyl-3-methyl-3-methylformazan. In the case of l,5.diphenylformazan, the reaction proceeds only in the second direction.See [3] for Communication II.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1704–1705, December, 1970.     

Total synthesis of aspidophytine

A total synthesis of aspidophytine was accomplished by employing a newly developed strategy for the enantiospecific syntheses of aspidosperma alkaloids. The key steps involve a novel ketene-lactonization reaction of a chiral vinyl sulfoxide (Marino annulation reaction) to set up the chiral quaternary carbon center, and a tandem Michael addition-alkylation reaction sequence to form the polycyclic core structure.     

Enantioselective synthesis of silanol

An enantioselective nucleophilic substitution reaction of achiral dialkoxysilane has been developed. The reaction proceeds with efficient stereocontrol on the silicon chirality center to give the enantioenriched silyl ether, which can be converted to the silanol without loss of enantiopurity. We have analyzed the steric course of the reaction by using DFT calculations and propose a transition state model to explain the observed enantioselectivity.     

Ytterbium-catalyzed synthesis of dihydropyridines

The reaction of anilines, benzaldehydes, and ethyl 3,3-diethoxypropionate in the presence of Yb(OTf)₃ proceeded under mild reaction conditions to give dihydropyridines (DHPs). We have found that the reaction depended on the solvent and the DHPs were obtained selectively in 1,4-dioxane as a solvent. Various 2,6-unsubstituted DHPs were synthesized in one pot in satisfactory yields.     

Total synthesis of leustroducsin B

Leustroducsin B was synthesized via a convergent route based on division of the leustroducsin molecule into three segments A, B, and C. Two coupling reactions (Julia coupling reaction and Nozaki-Hiyama-Kishi (NHK) reaction) were employed for coupling of segments A and B: segment A1 for the Julia coupling reaction was prepared by a combination of Sharpless asymmetric epoxidation and an epoxide-cleavage reaction with an organoaluminum reagent, while segment A2 for the NHK reaction was synthesized from optically active alcohol that had previously been prepared by lipase-catalyzed kinetic resolution. Segment B, whose structure was modified with some functional groups, was synthesized from (R)-malic acid by a combination of Wittig reaction and Sharpless asymmetric dihydroxylation, and segment C, containing a cyclohexane moiety, was prepared by asymmetric Diels-Alder reaction. Segment B was first coupled with segment A1 via the Julia coupling reaction, but the yield was low due to unexpected epimerization. The NHK reaction of segment A2 proceeded to give the coupling product in good yield. This product was coupled with segment C via Wittig and Stille coupling reactions, and finally, phosphorylation was carried out by partial hydrolysis of a cyclic phosphate to give leustroducsin B.     

Activated nitriles in heterocyclic synthesis. A novel synthesis of pyrazine derivatives

A novel synthesis of pyrazine derivatives from the reaction of α-tosyloximinonitriles with several active methylene enaminonitrile derivatives is reported. The reaction sequence is discussed.     

Total synthesis of panepophenanthrin

[reaction: see text] The biomimetic synthesis of the racemic dimer panepophenanthrin was achieved in good yield employing a tandem reaction sequence.     

A novel three-component butenolide synthesis

[reaction: see text]. 5-Acylamino butenolides can be assembled by a multicomponent reaction (MCR) of isocyanides, glyoxals, and acetophosphonic acid diethylesters, followed by a intramolecular Wittig-type reaction. The reaction can be performed either in one pot or with the isolation of the intermediate Passerini product. This versatile reaction offers three independent inputs displayed in the final product. Applications in combinatorial chemistry and natural product synthesis can be envisioned.     

Total synthesis of cruentaren B

A convergent total synthesis of the cytotoxic natural product cruentaren B is completed in 26 steps (longest linear sequence) with an overall yield of 7.1%. For the construction of the C1-C11 benzolactone fragment of the molecule, the key steps used were O-methylation, using a Mitsunobu reaction, a Stille coupling method to construct the C7-C8 bond, and a Brown's asymmetric crotylboration reaction for the direct enantioselective installation of the two chiral centers present in this fragment. For diastereoselective installation of the chiral centers in the C12-C20 polyketide fragment, an Evans syn aldol reaction on a chiral aldehyde, derived from methyl (R)-3-hydroxyl-2-methylpropionate, and subsequently a Mukaiyama aldol reaction were employed. For the construction of the C21-C28 tail, a "non-Evans" syn aldol reaction was used. The three fragments were coupled by an SN2 reaction and a Wittig olefination reaction followed by standard functional group manipulations to furnish the target molecule.     

双中心协同催化作用在不对称合成中的应用

介绍了双中心协同催化作用的概念以及A型和B型两类催化剂。综述了A型催化 剂在不对称硝基－类羟醛反应、迈克尔加成反应、亚胺和醛的氢膦酰化反应、曼尼 希反应、不对称醛酮羟醛反应以及环氧开环反应中的应用；同时简要介绍了B型催 化剂在不对称合成中的应用。     

膦酰肽和膦酰酯肽的汇聚式合成

本文首先介绍了膦酰肽的分类、结构特征以及膦酰肽的主要合成方法,然后详细介绍了类Mannich反应在合成氨基膦酸衍生物中的应用,并介绍了以类Mannich反应为关键步骤通过汇聚式的方法合成膦酰肽、膦酰酯肽、次膦酰肽、次膦酰酯肽、磺酰膦酰杂交肽的研究进展.汇聚式的合成方法具有原料简单、合成步骤少、原子经济性好等优点.     

Practical synthesis of azobenzenophanes

We devised a practical synthetic route to azobenzenophanes via successive Cu- and Pd-catalyzed coupling reaction of aryl hydrazide and aryl halide followed by Cu(I)-mediated oxidation reaction.     

Heterodiene synthesis

The reaction of trichloro- and trifluoroacetic acid amidines with aromatic aldehydes and the reaction of benzamidine with butyraldehyde yielded, respectively, 2-aryl-4,6,-bis(trichloromethyl)-, 2-aryl-4,6-bis(trifluoromethyl)-1,2-dihydro-sym-triazines, and 2-propyl-4,6-diphenyl-1, 2-dihydro-sym-triazine. The reactions of these compounds and the previously obtained sym-dihydrotriazines with acetylenedicarboxylic and propiolic acid esters were studied.See [1] for communication III.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 704–707, May, 1971.     

Total synthesis of salinosporamide A

The total synthesis of salinosporamide A has been achieved through enzymatic desymmetrization, diastereoselective aldol reaction, intramolecular aldol reaction, and intermolecular Reformatsky-type reaction followed by 1,4-reduction as key reactions.     

One-step synthesis of oxazolinoazetidinones from penicillin sulfoxides: potential intermediates for 1-oxacephem synthesis

Reaction of penicillin sulfoxides with a tervalent phosphorous compound in the presence of a catalytic amount of squaric acid gave oxazolinoazetidinones, potential intermediates for synthesis of 1-oxacephems, in good yields.2β-Chloromethyl- and 6α-methoxypenicillin sulfoxides also undergo this reaction. The reaction contrasts with the well-known Cooper reaction which usually gives thiazolinoazetidinones.     

Convergent synthesis of pyragonicin

This paper describes a second-generation synthesis of an antitumor tetrahydropyran (THP) acetogenin, pyragonicin. The key step involved an olefin cross-metathesis between the THP segment and the terminal gamma-lactone residue. The coupling reaction in the presence of Grubbs' second-generation catalyst resulted in an unseparable mixture of a desired coupling product and its one-carbon eliminated product while the use of Grubbs' first-generation catalyst afforded the former exclusively. A novel MOM-migrating reaction found in a cyclization reaction is also discussed.     

Concise synthesis of dl-febrifugine

Racemic compound (1) of the antimalarial agents febrifugine (d-1) was synthesized using an stereoselective Michael reaction of an omega-amidoenone (5) which was prepared by the Wittig reaction of piperidinediol (7).     

Direct synthesis of aromatic polyamides

The synthesis of aromatic polyamides, namely poly(p-phenylenetere-phthalamide) and poly(p-benzamide), via phosphorylation reaction has been thoroughly investigated. The effect of reaction temperature, concentration of monomers and reactants, type and concentration of salts, amount of the activator and its stepwise addition have been considered and the optimum reaction conditions found. The resultant synthesis of the above polymers, also in connection with the high purification techniques of all components of the reaction mixture, allowed to reach the highest molecular weights obtained so far by this synthetic way.