Synthesis of 4-aminomethyl-tetrahydrofuran-2-carboxylates with 2,4-cis and 2,4-trans relationships

Templated tetrahydrofuran-based γ-azido esters were prepared with the C-2 and C-4 functionalities in cis and trans relative configurations. This was achieved by ring contraction of the suitably protected 2-O-triflates of pentono-1,5-lactones (d-ribose and l-arabinose) with subsequent introduction of the azide via the 4-O-triflate. Access to a corresponding β-azido ester was achieved in good yield. Little elimination product was observed by introduction of the azide via the 3-O-triflate. These azido esters are scaffolds, which may be predisposed to adopt secondary structural motifs, for example, for use as peptidomimetics; they may also be utilised for the preparation of stereodiverse compound libraries.     

Stereoselective synthesis of the various isomers of 3,4-dideoxy furanoid sugar amino acids with methyl substitution at the C6 position

Various isomers of C6-methyl-containing chiral 3,4-dideoxy furanoid sugar amino acids were synthesized following a common strategy, in which the C2 and C6 chiral centres were derived from the chiralities of the two starting materials, glyceraldehyde acetonide and N,N-dibenzylalaninal, respectively, and the C5 centre was fixed by standard diastereoselective transformations.     

Recent progress of sugar amino acids: Synthetic strategies and applications as glycomimetics and peptidomimetics

In order to meet the increasing demands for the development of large varieties of new molecules for discovering new drugs and materials, organic chemists are developing many novel multifunctional building blocks, which are assembled rationally to create ‘nature-like' and yet unnatural organic molecules with well-defined structures and useful properties. Sugar amino acids(SAAs), the carbohydrate derivatives bearing both amino and carboxylic acid functional groups, are important ones of these multifunctional building blocks, which can be used to create novel materials with potential applications as glycomimetics and peptidomimetics. This review will focus on recent synthetic strategies of SAAs and their applications in creating large number of structurally diverse glycomimetics and peptidomimetics.     

A study of polychlorinated leucine derivatives: synthesis of (2S,4S)-5,5-dichloroleucine

The first total synthesis of (2S,4S)-5,5-dichloroleucine has been achieved in 11 steps from l-pyroglutamic acid. A key step is the dichlorination process on the hydrazone of aldehyde 13 with CuCl₂ in triethylamine.     

Synthesis of 4-monofluoromethylenyl- and cis-4-monofluoromethyl-l-pyroglutamic acids via a novel dehydrofluorination

Novel dehydrofluorination reactions accidentally found were used to synthesize terminal monofluoro olefin lactam analogues in good yield. The following hydrogenation of the resulting defluorinated product was systematically investigated. Two important fluorinated amino acids: 4-monofluoromethylenyl-l-pyroglutamic acid 16 and cis-4-monofluoromethyl-l-pyroglutamic acid 17 were synthesized using the methodology.     

A novel four-component synthesis of ethyl 6-amino-4-aryl-5-cyano-2,4-dihydropyrano[2,3-c]pyrazole-3-carboxylates

Ethyl 6-amino-4-aryl-5-cyano-2,4-dihydropyrano[2,3-с]pyrazole-3-carboxylates were synthesized via a four-component reaction of the sodium salt of diethyloxaloacetate, an aromatic aldehyde, hydrazine hydrate, and malononitrile. The products were obtained in moderate to high yields.     

Efficient and stereoselective synthesis of novel cis-4-substituted proline analogues

A series of novel cis-4-substituted proline analogues were designed and synthesized. Highly stereoselective alkylations at the γ-position of glutamic ester 2 were achieved, followed by reduction, mesylation, and cyclization to afford the title compounds 1 in good yields and high diastereoselectivity.     

Structure and stereochemistry of maytensifolin-a,a novel hydroperoxy-nortriterpene from maytenus diversifolia

The structure and stereochemistry of the first hydroperoxy triterpene, maytensifolin-A, isolated from maytenus diversifolia, have been established from spectral and single-crystal X-ray analyses.     

Pleated Sheets and Turns of β-Peptides with Proteinogenic Side Chains

Components of a toolbox with predictable secondary structural elements: β-peptides. The β-peptide shown here with proteinogenic side chains adopts a parallel pleated sheet structure in the solid state upon incorporation of suitably configured β-amino acids. When a β-dipeptide turn segment is incorporated in the center, a hairpin is formed in solution.     

Design and synthesis of (E)-4-((3-ethyl-2,4,4-trimethylcyclohex-2-enylidene)methyl)benzoic acid

(E)-4-((3-Ethyl-2,4,4-trimethylcyclohex-2-enylidene)methyl)benzoic acid, 6, was synthesized in 87% starting from β-cyclocitral. The target compound 6 was synthesized starting from 1 via a Grignard reaction to form alcohol 2. Compound 2 was converted to Wittig salt 3 by treatment with aldehyde 4 in butyllithium and hexane at −78 °C to form ester 5. Ester 5 was saponified and, following acidification, acid 6 was isolated as white solid yield 87%.     

Stereoselective synthesis of highly functionalized thiopeptide thiazole fragments from uronic acid/cysteine condensation products: access to the core dipeptide of the thiazomycins and nocathiacins

We present the stereoselective synthesis of various highly functionalized thiazole dipeptides that are found in thiopeptide antibiotics like thiazomycins and nocathiacins. The condensation of an uronic acid with l-cysteine methyl ester delivers along two different protocols the stereopure thiazolidine lactones or lactams on the multigram scale, respectively. Oxidation of the thiazolidine moiety to the thiazole and tailoring of the sugar chains yield the thiazole dipeptide as present in the core motif of the thiopeptide antibiotics, as well as its epimer and a homolog. The modular assembly of the potent natural products and their analogs relies on the synthetic accessibility of adequately protected building blocks of tailored absolute stereochemistry.     

4-Hydroxyquinolones-2. 91. Synthesis and properties of ethyl 1-R-4-hydroxy-6-methyl-2-oxo-dihydropyridine-5-carboxylates

The reaction of ethyl aminocrotonates with derivatives of malonic acid is a suitable method for the preparation of ethyl 4-hydroxy-6-methyl-2-oxo-1,2-dihydropyridine-5-carboxylates. One of the synthesized materials has been studied by X-ray crystallography. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, 217–223, February, 2006.     

A novel convenient approach to the synthesis of 2-substituted analogs of ornithine and homolysine

A novel efficient method for the synthesis of earlier unknown 2-substituted analogs of ornithine and homolysine from substituted 5-aminopentyl- and 3-midopropylhydantoins (prepared from cyclic imines and amino and amido ketones) was developed. Hydrolysis of hydantoins with a solution of Ba(OH)₂ gave the target amino acids in high yields.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2749–2753, December, 2004.     

Synthesis of protected (2R,3R,4S)-4,7-diamino-2,3-dihydroxyheptanoic acid, a constituent of callipeltins A and D

An efficient synthesis of protected (2R,3R,4S)-4,7-diamino-2,3-dihydroxy heptanoic acid, a constituent of the depsipeptides, callipeltins A and D from l-ascorbic acid is described.     

磷酸三乙胺-乙腈流动相体系反相分离2，4-二硝基氟苯-氨基酸衍生物

从两个方面改进了反相分离2,4-二硝基氟苯-氨基酸衍生物测定氨基酸的分析方法：一是使用高缓冲容量pH 2.75和6.50的磷酸三乙胺-乙腈流动相体系代替醋酸盐/乙腈流动相体系;另一个是强调了衍生反应的操作细节。以含精、丝、天冬、谷、苏、甘、丙、脯、组、蛋、缬、色、苯丙、亮、异亮、赖、酪氨酸注射液为目标试样,对方法进行认证,线性不低于0.9999(对谷氨酸、赖氨酸和酪氨酸不低于0.9998),准确度（回收率）为100±1%,精密度（RSD）低于0.5%,均优于以往的方法。方法适用于在一般液相色谱实验室进行氨基酸注射液和原料药的分析,无需专用氨基酸分析仪。     

Structure and stereochemistry of paristerone,a novel phytoecdysone from the tubers of paris polyphylla

Paristerone, a novel phytoecdysone has been isolated from the tubers of P. polyphylla and its structure and stereochemistry has been established as 2α, 3β, 14α, 20(R), 22(r), 25-hexahydroxy-5β-chloest-7-en-6-one (2-epiecdysterone) on the basis of chemical and physical evidence.     

A versatile synthesis of 2-substituted 4-amino-1,2,4,5-tetrahydro-2-benzazepine-3-ones

A mild and general strategy for the synthesis of 2-substituted 4-amino-1,2,4,5-tetrahydro-2-benzazepine-3-ones is described. The seven-membered lactam is prepared by intramolecular amide bond formation from the intermediate amino acid, which is obtained either by reductive alkylation of a variety of amines with N-Boc,N-Me-ortho-formyl-Phe and Phth-ortho-formyl-Phe, or by reductive amination of a variety of aldehydes with N-Boc-ortho-aminomethyl-Phe.     

Structure and stereochemistry of mexicanin F,a novel dimeric nor-sesquiterpene lactone from Helenium mexicanum

The structure and stereochemistry of mexicanin F, a novel dimeric nor-sesquiterpene lactone isolated from Helenium mexicanum, have been stablis$\text{h}$ed from spectral and single-crystal x-ray analyses.     

A novel, one-pot, solvent-, and catalyst-free synthesis of 2-aryl/alkyl-4(3H)-quinazolinones

A novel and one-pot synthesis of 2-aryl/alkyl-4(3H)-quinazolinones is described. The in situ prepared amidoximes from the reaction between nitriles and hydroxylamine are condensed with anthranilic acids under solvent- and catalyst-free conditions to produce the title compounds in excellent yields.