Enantioselective one-pot synthesis of 2-amino-4-(indol-3-yl)-4H-chromenes

An enantioselective one-pot synthesis of 2-amino-4-(indol-3-yl)-4H-chromenes via a Knoevenagel/Pinner/Friedel-Crafts reaction of salicylaldehyde, malononitrile, and indole is presented. Moderate to good yields (up to 89%) and high enantioselectivities (up to 90% ee) were obtained with an N,N'-dioxide-Zn(II) complex as the catalyst. This strategy provides an efficient and convenient method to access enantiomerically enriched 2-amino-4H-chromene derivatives.     

1-Amino-3-alkyl-2-(methylthio)benzimidazolium salts: synthesis,reaction with CH-acid anions,and conversion to pyrazolo[1,5-a]benzimidazole derivatives

For the first time, 1-amino-3-alkylbenzimidazolinethiones were obtained by heating 1-amino-3-alkylbenzimidazolium iodides with sulfur in the presence of triethylamine. They were converted to 1-amino-3-alkyl-2-(methylthio)benzimidazolium salts, which, during reaction with CH-acid onions, gave the corresponding 1-amino-3-alkyl-2-methylenebenzimidazoline derivatives. Under conditions of alkaline or acid catalysis, the latter derivatives cyclized to 2-amino- or 2-hydroxy derivatives of pyrazolo[1,5-a]benzimidazole.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 205–214, February, 1992.     

An efficient one-pot synthesis of 1,4-disubstituted 3-amino-2-pyridone derivatives via three-component reactions of alkynyl aldehydes and amines with ethyl 2-((diphenylmethylene)amino)acetate

A facile and efficient one-pot synthesis of 1,4-disubstituted 3-amino-2-pyridone derivatives via three-component reactions of readily available alkynyl aldehydes, amines, and ethyl 2-((diphenylmethylene)amino)acetate has been developed. The alkynyl aldehyde substrates and the amine partners can be flexibly varied to achieve a range of 3-amino-2-pyridone derivatives, which could exert interesting chemical and biological properties. The reaction mechanism for the formation of 3-amino-2-pyridone derivatives is briefly explained.     

Reaktionen mit γ-Chloracetessigesterderivaten

Reactions with derivatives of γ-chloroacetoacetic acid Ethyl γ-chloroacetoacetate reacts with ammonia to give ethyl β-amino-γ-chloro-crotonate; with aniline, however, β-anilino-crotonic acid γ-lactone is formed. The reaction of ethyl α-cyano-γ-chloro-acetoacetate with arylamines yields 1-aryl-2-amino-3-ethoxycarbonyl-pyrrolin-4-ones.     

The synthesis of DL- and L-2-amino-3-fluorobutyric acid

DL- and L-Threonine were esterified to their methyl and ethyl esters which on treatment with sulfur tetrafluoride in anhydrous hydrogen fluoride gave DL- and L-methyl and ethyl 2-amino-3-fluorobutyrates, respectively. Both fluorinated esters afforded on hydrolysis DL- and L-2-amino-3-fluorobutyric acid, respectively.     

Synthesis of some derivatives of 3-amino-3-desoxyerythrose and 3-amino-3-desoxy-D-3-erythrose

The synthesis of derivatives of 3-amino-3-deoxy-L-erythrose by LAH or LAD reduction of the oxime of 1,2-O-isopropylidene α-L -glycero-tetros-3-ulofuranose is described.     

Solid-phase synthesis of substituted 3-amino-3′-carboxy-tetrahydrocarbazoles

Two related solid-phase synthesis routes have been developed allowing the synthesis of 3-amino-3′-carboxy substituted tetrahydrocarbazole derivatives. Diversity can be introduced at the amino and carboxy functionalities and at the nitrogen and the aromatic ring of the tetrahydrocarbazole moiety. Both routes rely on Fmoc-protected 1-amino-4-oxocyclohexanone carboxylic acid as central core element. Derivatization of the carboxy function is achieved with amines, derivatization of the amino functionality is possible by reaction with alkyl halides, isocyanates, activated alcohols, sulfonic acid chlorides or carboxylic acids. The tetrahydrocarbazole scaffold is generated by Fischer indole cyclization with phenyl hydrazine derivatives, thereby introducing diversity in the aromatic moiety. N-Alkylation at the indole nitrogen with alkyl halides delivers N-substituted derivatives.     

Derivatives of 4-amino-4H-1,2,4-triazole-3-thiols linked to the pyrrole cycle and some products of their S-alkylation

This study offers an access to 21 new heterocyclic compounds representing pyrrole derivatives of 4-amino-4H-1,2,4-triazole-3-thiols or 1,3,4-oxadiazole-2-thiols. The principal synthetic approach is based on the cyclization of substituted potassium 2-(pyrrolecarbonyl)hydrazine-1-carbodithionate with hydrazine hydrate to 5-(substituted pyrrolyl)-4-amino-4H-1,2,4-triazole-3-thiols, followed by S-alkylation with methyl iodide or benzyl chloride. Among the resulted thirteen S-alkyl derivatives, five 1,3,4-oxadiazole derivatives have been isolated as secondary products and their formation is explained as being the result of S-alkylation of intermediate 1,3,4-oxa-diazole-2-thiols, generated in the alkaline medium. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 383–391, March, 2007.     

3-Formylcyclopent-3-enyl- and 3-carboxycyclopentylglycine derivatives: a new stereocontrolled approach via retro-aldol or retro-Claisen reactions

A new synthetic approach to diastereomeric cyclopent-3-enylglycines 19/20, functionalized on the ring with a formyl group, and to cyclopentylglycine, substituted with a carboxy group (compounds 21/22), was devised by applying retro-aldol and retro-Claisen reactions, respectively, to diastereomeric 2-amino-3-ethoxycarbonyloxynorbornene-2-carboxylic acid derivatives 5, 6 and to diastereomeric 2-amino-3-oxo-norbornane-2-carboxylic acid derivatives 17, 18. The goal of controlling the cis stereochemistry of the cyclopentyl substituents was reached using compounds 17, 18. A partial control of the stereochemistry of the amino acidic carbon was achieved starting from 17 and using sodium hydrogen carbonate in acetone/DMF. From exo-17, the acid 22 was obtained as the major diastereomer.     

A facile synthesis of 3-amino-5-substitutedaminoisothiazole-4-carboxylic acid derivatives

A facile, general and one-pot method for the preparation of 3-amino-5-substituted-aminoisothiazole-4-carboxylic acid derivatives, in high yields, by the aminative cyclization of 3-amino-3-mercaptoacrylonitriles is described.     

An approach to sequence-specific antibody proteases

We describe here a novel strategy for the isolation of antibodies with sequence-specific protease activity: the synthesis of dipeptide haptens in which the targeted peptide bond has been replaced by a ring-strained or torsionally strained hydroxyethylene transition-state analog. Thus, the analogs mimic both a peptide bond in a distorted, reactive conformation and the transition state for peptide bond hydrolysis. In order to obtain sequence-specific antibody proteases, these analogs have been flanked with additional amino acid residues in preparation for immunization. In particular, we have synthesized peptides containing analogs such as 2-cis-amino-3-cis-hydroxycyclobutane carboxylic acid andendo-(3-amino-2-hydroxy)bicyclo[2.2.1]heptane-7-anti-carboxylic acid. We have also prepared a series of peptide derivatives containing analogs, such as 2-[3-amino-2-oxo-1-azetidinyl]-3-methylbutanoic acid, in which the targeted peptide bond has been incorporated into a β-lactam ring. Since the “peptide bond” has been left intact, these species mimic only a distorted ground state. At present, antibodies are being elicited against a number of the above peptide derivatives.     

靛红亚胺参与构建手性3-氨基-2-吲哚酮骨架的研究进展

手性3-氨基-2-吲哚酮骨架广泛存在于许多药物分子以及天然产物中,具有较高的药用价值。 靛红亚胺参与的不对称反应是合成手性3-氨基-2-吲哚酮衍生物的直接途径。 本文围绕着不对称aza-Henry反应、不对称环化反应及其他不对称反应3个方面,综述了靛红亚胺参与构建手性3-氨基-2-吲哚酮衍生物的研究进展并进行了展望。     

From BN-Naphthalenes to Benzoborole Dianions

The synthesis of benzoborole dianions by alkali metal reduction of BN-naphthalene derivatives via a ring-contraction strategy has been developed. Reduction of 1-alkynyl 2,1-benzazaborine 1 a in Et₂O led to the elimination of alkynyllithium with the formation of 1-amino-1-benzoborole trilithium salt 2 a , whereas reduction of 1-phenyl 2,1-benzazaborine 1 c in THF yielded 1-phenyl-1-benzoborole dilithium salt 2 c with the elimination of ArNHLi. The trilithium and dilithium salts 2 a and 2 c have been fully characterized. Treatment of trilithium salt 2 a with Et₃NHCl led to the selective protonation of the amino lithium to afford the dilithium salt 2 aH , which could be cleanly oxidized to 1-amino-1-benzoborole 3 in an excellent yield. Reaction of 1-phenyl-1-benzoborole dilithium salt 2 c with MeI yielded the lithium borate 4 c , which is luminescent both in solution and in the solid state.     

On triazoles. VIII The reaction of 5-amino-1,2,4-triazoles with ethyl 2-cyano-3-ethoxyacrylate and 2-cyano-3-ethoxyacrylonitrile

The reaction of different 5-amino-3-Q-1H-1,2,4-triazoles 1 with ethyl 2-cyano-3-ethoxyacrylate ( 5a ) and 2-cyano-3-ethoxyacrylonitrile ( 5b ) to yield either the a type 5-amino-, or the b type 7-amino-1,2,4-triazolo[1,5-a]-pyrimidine derivatives 6–10 was studied. The structure of compounds 6 and 9 was proved by their degradation to the corresponding derivatives 17a and 18a , respectively, through intermediates 11a, 12a, 13a, 14a, 15a and 16a , respectively. The structure of derivatives 7, 8 and 10 was proved on the basis of the analogy of their uv spectra with those of 6a and 9a , respectively. The isolation of the intermediates 19 and 20 helped to prove the mechanism of the reactions leading to the formation of 6a and 9a , respectively. In the reaction of the N-substituted 5-amino-1,2,4-triazoles with 5a the expected condensed ring products were not formed. Instead the aminoacrylates 22 and 24 were obtained. The “Z”-“E” isomeric structure of derivatives 19, 20, 22 and 24 was proved with the help of their pmr spectra. The “Z” isomeric structure of the thermodynamically stabile 22 was corroborated with the help of its proton coupled cmr spectra, too.     

Organocatalytic and direct asymmetric vinylogous Michael addition of 3-cyano-4-methylcoumarins to α,β-unsaturated ketones

The first highly regio-, chemo-, and enantio-selective direct vinylogous Michael addition of 3-cyano-4-methylcoumarin derivatives to α,β-unsaturated ketones is described, employing readily available 9-amino-9-deoxy-epiquinine as the iminium organocatalyst.     

Conjugate addition of amines to chiral 3-aziridin-2-yl-acrylates

Conjugate addition of benzylamine to chiral methyl cis-3-aziridin-2-yl-acrylates was successfully proceeded to yield 3-aziridin-2-yl-3-benzylaminopropionates in high yield with high stereoselectivity. The addition products were used for the asymmetric synthesis of vicinal diamine derivatives including 4-amino-5-methylpyrrolidin-2-one, 3,4-diaminopentanoate, and 5-chloromethyl-4-alkoxycarbonylmethylimidazolidin-2-one.     

Synthesis of functionalized allylic sulfoxides and their use in the construction of 2,3,4-trisubstituted furans via a [3 + 2] annulation

A route to 2,3,4-trisubstituted furan derivatives based on a [3 + 2] annulation of functionalized allylic sulfoxides and aldehydes is described. In this strategy, the precursors of allylic sulfoxides 4, allylic sulfides 3, were synthesized via a thiomethylation reaction of an alpha-EWG ketene-S,S-acetal 1 (EWG: electron-withdrawing group), formaldehyde, and a thiol 2 in high to excellent yields. Allylic sulfoxides 4 were prepared by a highly regioselective oxidation of 3, using m-chloroperoxybenzoic acid as oxidant. Thus, starting from these readily available sulfoxides 4, 2-alkylthio-3,4-disubstituted furans 6 were efficiently constructed via the [3 + 2] annulation reaction of 4 with aldehydes 5 under mild conditions. Further replacement of the 2-alkylthio group of 6 with amines led to the formation of 2-amino-3,4-disubstituted furan derivatives 7.     

Heterocyclic β-Enamino esters. 28. The reaction of heterocyclic β-Enamino esters and nitriles with cyclic amidines. A simple route to azolopyrimidines

Whereas 2-amino-3-ethoxycarbonyl-4,5-dihydrofurans Ia-c condense with 5-membered amidine derivatives, via elimination of ethanol to afford the azolopyrimidines IIIa,b, XI, and XIVa,b, the 2-amino-3-cyano-4,5-dihydrofurans Id,e give with the same reagents, under elimination of ammonia, the novel ring systems of furo-azolopyrimidines XVIII and XXa,b. 2-Amino-3-ethoxycarbonyl-5,6-dihydro-4H-thiopyrane (XXI) reacts with 5-amino-1,2,4-triazole (II) to yield the triazolo[1,5-a]pyrimidine XXII, and with 2-aminobenzimidazole to XXIII. The mechanism of these reactions is discussed. XIVb and VIIb are cyclized in a secondary step to give the novel furo[2,3-d]benzimidazo[1,2-a]pyrimidine XXVI, and furo[2,3-d]-1,2,4-triazolo[1,5-a]pyrimidine XXVIII respectively, besides the acetoxy derivatives XVII and XXIX.     

Synthesis and Reactivity of Azidoximes: III. 1-Azido(4-amino-1,2,5-oxadiazol-3-yl)aldoxime in the Cycloaddition Reaction

By 1,3-dipolar addition of 1-azido(4-amino-1,2,5-oxadiazol-3-yl)aldoxime to propargyl alcohol and phenylacetylene bicyclic 4-amino-1,2,5-oxadiazol-3-yl(4-R-1,2,3-triazol-1-yl)ketoximes were obtained which in reaction with acetic anhydride afforded the corresponding O-acyl derivatives. Diazotization of 4-amino-1,2,5-oxadiazol-3-yl(4-R-1,2,3-triazol-1-yl)ketoximes furnished 4-azido derivatives. The treatment of 4-amino-1,2,5-oxadiazol-3-yl(4-hydroxymethyl-1,2,3-triazol-1-yl)ketoxime with SOCl₂ resulted in 4-amino-1,2,5-oxadiazol-3-yl(4-chloromethyl-1,2,3-triazol-1-yl)ketoxime, whose chlorine atom was readily replaced by azide ion affording 4-amino-1,2,5-oxadiazol-3-yl(4-azidomethyl-1,2,3-triazol-1-yl)ketoxime.     

Preparation of new nitrogen-bridged heterocycles 72. A new approach to 1-acyl-3-(substituted methylthio)thieno[3',4':4,5]imidazo[1,2-a]pyridine derivatives. [corrected

The alkaline treatment of the pyridinium salts, readily available from the S-alkylations of 3-amino-4-(1-pyridinio)thiophene-5-thiolates with various alkyl halides, in chloroform at room temperature afforded the corresponding thieno[3',4':4,5]imidazo[1,2-a]pyridine derivatives in low to moderate yields via the intramolecular cyclization of the resulting 1,5-dipoles followed by the aromatization of the primary cycloadducts. Interestingly, the reactions using unsymmetrical 3-amino-4-[1-(3-methylpyridinio)]thiophene-5-thiolates afforded only 8-methylthieno[3',4':4,5]imidazo[1,2-a]pyridines and the other 6-methyl derivatives were not formed at all. In addition the isolation of a byproduct in the condensation reaction of pyridinium salt with the solvent (CHCl?) is also discussed.