Stereoselective synthesis of pseudotripeptides incorporating uncommon bis-α-aminoacid derivatives and X-ray analysis. Part 3

Stereoselective synthesis of pseudotripeptides 4, 5, 6, 8, 9, 13 and 14, incorporating an uncommon bis(α-aminoacid) derivative, has been accomplished starting from the L-valine derived chiral synthon 1. The configuration of the introduced stereogenic centres has been assigned on the basis of ¹H NMR spectroscopic data. The geometry of the tripeptides, deduced on the basis of ¹H NMR parameters and IR spectra, was confirmed by X-ray crystal structure analysis of 6.     

Stereocontrolled synthesis of enantiomerically pure unsaturated analogues of 2,6-DAP. Part 5

An efficient new stereocontrolled synthesis of (2R,6R)-(+)- and (2S,6S)-(−)-2,6-diamino-4-methylene-1,7-heptanedioic acid 8a and 9a, respectively, has been accomplished starting from the glycine-derived chiral synthon 1. The enantiomerically pure α-alkyl derivatives 8b–d and 9b–d have also been synthesized. The absolute configuration of the new stereocenters was assigned on the basis of ¹H NMR spectra.     

Alkaloids of NIRAM,natural dye from Polygonum tinctorium,and their anti-inflammatory activities

Phytochemical investigation of EtOH extract of NIRAM, natural dye from Polygonum tinctorium, resulted in the purification of nine alkaloid compounds (1–9) including four new compounds (1–4). Structures of these new compounds were elucidated by 1D and 2D NMR (¹H and ¹³C NMR, ¹H–¹H COSY, ¹H–¹³C HSQC, ¹H–¹³C HMBC), IR, UV, HR-ESI-MS, and ECD spectra. Isolated compounds (1–9) were tested for their inhibitory effects on nitric oxide (NO) production in lipopolysaccharide (LPS)-activated BV-2 cells. Compounds 1–3, 5, and 7 showed potent NO production inhibitory activities, with IC₅₀ values of 3.88–22.87 μM.     

Synthesis of enantiomerically pure spiro-cyclopropane derivatives containing multichiral centers

A novel chiral source, 5-(R)-[(1R,2S,5R)-(−)-menthyloxy]-3-bromo-2(5H)-furanone (5a), was obtained in 46% yield with d.e.≥98% from the epimeric mixture of 5-(l-menthyloxy)-3-bromo-2(5H)-furanone (5a+5b) obtained via the bromination of an epimeric mixture of 5-(l-menthyloxy)-2(5H)-furanone (3a+3b) followed by the elimination of hydrogen bromide. The asymmetric reaction of 5a with a nucleophilic alcohol afforded enantiomerically pure spiro-cyclopropane derivatives containing four stereogenic centers, 9a–9e, in 50–68% yield with d.e.≥98%. The enantiomerically pure compounds 9a–9e were identified on the basis of their analytical data and spectroscopic data, such as [α]_D²⁰, UV, IR, ¹H NMR, ¹³C NMR, MS and elementary analysis. The absolute configuration of the chiral spiro-cyclopropane compound 9a was established by X-ray crystallography.     

Reaktionen von o-halogenacetophenonen mit schwefelkohlenstoff und phenylisothiocyanat

O-Haloacetophenones 1 react with carbon disulfide in the presence of sodium hydride and an alkylating reagent to ketene S,S-acetals 3 and 4. The formation of 1-thiochromones 5 is possible, when the reaction is carried out at 100°. Treatment of 3a with aniline and guanidine, respectively, leads to the ketene N,N-acetal 6 and the 2-aminopyrimidine 7, respectively Reaction of 1 with phenyl isothiocyanate/sodium hydride and following alkylation gives ketene S,N-acetals 9, thiazolidones 14 and thiazolidine 15. Cyclisation of 9 in a basic medium forms the 4(1H)-quinolones 11. The physical properties of synthesized compounds are characterized by means of mass, ¹H NMR, and IR spectra. The possible modes of formation are discussed.     

A study of the reaction of 2-thiazolin-4-ones with some electrophiles under microwave irradiation versus conventional condition

Coupling of 5-dimethylaminomethylene-3-methyl-2-(pyridine-2-ylimino)-thiazolidin-4-one (3) with diazotized methyl anthranilate afforded the 3-methyl-5-(2-methoxycarbonylphenylhydrazono)-2-pyridine-2-ylimino)thiazolidin-4-one (5). Reaction of 2-(arylamino)thiazol-4-ones 1a,b with arylidenemalononitriles under microwave irradiation gave 2-substituted amino-5-arylidenethiazolin-4-ones 9a–f. Alternatively, compound 9 could also be obtained by reacting compound 1 with aromatic aldehydes. Treatment of compound 9 with acetic acid yielded the corresponding thiazolin-2,4-diones 10. However, the reaction of 1 with cyanoacetic acid yielded the corresponding 4-cyanoacetyl derivative 12, in good yield. The ¹H, ¹³C NMR spectra of some representative products and X-ray crystal structure determination are discussed.     

Crotocaudin; a rearranged labdane type norditerpene from Croton caudatus geisel

The structure and stereochemistry of crotocaudin, a new norditerpene occurring as a minor constituent in Crotoncaudatus Geisel (Euphorbiaceae) have been established as ent-8S,10S-15,16-epoxy-19-norcleroda-4,11,13(16), 14-tetraene 18,6S: 20,12-diolactone 7 from the detailed studies of ¹H NMR spectra using lanthanide shift reagents, decoupling experiments and chemical reactions. The congener, teucvidin, ent-10S-15,16-epoxy-19-norcleroda-4,13(16), 14-triene-18,6S: 20,12R-diolactone 1 was obtained as a major component besides several triterpenoids viz taraxerone 2, taraxerol 3 and taraxeryl acetate 4. ¹³C NMR and ¹H NMR spectra and a few novel reactions of teucvidin and its conversion to teucvin, ent-(6R,12R)-15,16-epoxy-19-nor-9,4-friedolabda-4,13(16),14-triene-18,6:20, 12-diolactone 6 are also reported.     

Synthesis and evaluation of in vitro antibacterial activity of novel 2,5-disubstituted-1,3,4-thiadiazoles from fatty acids

A series of new 1-（alkenoyl/hydroxyalkenoyl）-4-benzoyl-thiosemicarbazides 2a-d and 2-benzamide-5-alkenyl/hydroxyalk- enyl-1,3,4-thiadiazoles 3a-d were synthesized from fatty acid hydrazides. Structure of all these compounds was confirmed by IR, IH NMR, Sac NMR, mass spectra and elemental analysis. The bioassay results indicate that some compounds 2e, 2d, 3e and 3d have good antibacterial activity.     

N-[2-(1H-吲哚-3)乙基]-2-乙酰噻唑-4-甲酰胺及其类似物的合成

N-[2-(1H-吲哚-3)乙基]-2-乙酰噻唑-4-甲酰胺是最近从海洋细菌中分离得到的一种新型的天然杀藻剂, 以D-丙氨酸为原料合成了该化合物, 并用类似的方法首次合成了它的类似物2, 3和4. 其关键步骤为通过将取代的4-噻唑甲酸制成混酐与色胺连接的偶联反应. 各中间体都通过¹H NMR和¹³C NMR得到证实. 最终产品通过¹H NMR, ¹³C NMR和HRMS证实, 与文献所报道相一致.     

Stereocontrolled synthesis of unnatural cyclic dipeptides containing an l-valine unit

Stereoselective synthesis of unusual nonproteinogenic dipeptides 7a,b,d,e and h and 13b and i, containing an l-valine unit and a cyclic unnatural α-amino acid, has been accomplished starting from the l-valine derived chiral synthon 1. The absolute configurations of the new stereocentres were assigned on the basis of ¹H NMR spectra.     

Interaction entre groupes aromatique et polaire voisins—III: Synthese et etudes physico-chimiques d'acides p-x-phenyl-3 bicyclo[2.2.1] heptene-5 carboxyliques-2 et de leurs esters methyliques

The synthesis, ¹H and ¹³C NMR spectra of acids 1 to 4 and methyl esters 5 to 8 are described. Interaction of aromatic and polar groups in the cis acids must be steric in origin and not due to charge transfer complex or hydrogen bonding. The structure of 1e,3a,5e and 7e has been determined by X-Ray crystallography. ¹H and ¹³C NMR studies indicate that, in the cis compounds, the proximity of aromatic and polar groups tend to impose to them some largely predominant conformations which should be analogous in the crystal or in solution.     

Factors affecting stability and equilibria of free radicals—IX: Non-equivalence of aryl groups in 1,1-diaryl-2-benzenesulphonyl-hydrazyls and related compounds

1,1-Bis-(3',5'-di-t-butylphenyl)-2-benzenesulphonyl-hydrazine 11 and the corresponding 2-picryl-hydrazine 13 were synthesized. Oxidation of 11 afforded the stable hydrazyl 12 whose ESR spectrum could be simulated in terms of three hyperfine coupling constants. These experimental data leave no alternative but to assign larger proton hyperfine coupling constants to one aryl group in 12 than to the other. This non-equivalence was interpreted in terms of the Linnett theory. The picrylhydrazyl 14 does not give completely resolved ESR spectra. Structures were ascertained by IR, UV-vis, ¹H NMR and ¹³C NMR spectra.     

Synthesis and different substituent effects on spectral and electrochemical properties of porphyrin nicotinic acid binary compounds

The porphyrin nicotinic acid binary compounds with different substituents in porphine rings (5-(4-nicotinicoxyldecyloxy)phenyl-10,15,20-triphenylporhyrin 2a, 5-(4-nicotinicoxyldecyloxy)phenyl-10,15,20-tri(4-chlorophenyl)porphyrin 2b and 5-(4-nicotinicoxyldecyloxy)phenyl-10,15,20-tri(4-methoxyphenyl)porphyrin 2c) were synthesized. All of them have been characterized, assigned and analyzed by UV–vis, IR, MS and ¹H NMR spectra. Their electrochemical and spectroscopic properties were studied by using cyclic voltammetry, fluorescence spectra and Resonance Raman spectra. Different substituents have a little influence on electrochemical behavior and fluorescence spectra. In the Resonance Raman spectra, the substituent has little influence on the skeleton vibration of porphyrin and has much influence on the vibration of phenyl.     

Synthesis and conformational analysis of some cyanomethylene derivatives of piperidines

Five 4-dicyanomethylene derivatives 6–10, N-cyanoacetyl-cis-2,6-diphenylpiperidin-4-one 11 and 4-cyano(ethoxycarbonyl)-methylene-cis-2,6-bis(o-chlorophenyl)piperidine 12 were synthesised by condensing the appropriate piperidin-4-ones 13–17 with malononitrile/ethylcyanoacetate and their ¹H and ¹³C NMR spectra were recorded. The ¹H-¹H COSY spectrum for 6 and NOESY spectra for 8, 10, and 11 were also recorded. Based on coupling constants and the results obtained from NOESY spectra boat conformation for 10 and epimerised chair conformations for 8 and 9 have been proposed. Other derivatives adopt normal chair conformations. Theoretical calculations and the ¹H and ¹³C chemical shifts also support the above conformations. Mass spectra were also recorded for 6–12.     

Homolytic substitutions in indolinone nitroxide radicals—II: Reaction with organic peracids

The reactions of indolinone nitroxides 7 and of the corresponding amine precursors 15 with organic peracids were studied, and were found to give substitution products at the aromatic nucleus, i.e. 5-aroyloxy- and 7-aroyloxynitroxides 8 together with N-oxides 10 and with 7-hydroxynitroxides 9. Structures were assigned on the basis of ESR and ¹H NMR spectra. A reaction scheme was proposed involving a homolytic substitution which accounts for the products obtained and is supported by an experimental proof.     

Synthesis,characterization and in vitro antimicrobial screening of quinoline nucleus containing 1,3,4-oxadiazole and 2-azetidinone derivatives

A series of 3-chloro-1-(aryl)-4-(2-(2-chloro-6-methylquinolin-3-yl)-5-(pyridin-4-yl)-1,3,4-oxadiazol-3(2H)-yl)-4-ethyl-azetidin-2-ones (V)_1–12 have been synthesized and characterized by IR, ¹H NMR, ¹³C NMR and mass spectra. Synthesized compounds were screened for their antibacterial activity against four different strains like Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and Streptococcus pyogenes, while antifungal activity was determined against three different strains like Candida albicans, Aspergillus niger and Aspergillus clavatus. On the basis of statistical analysis, it has been observed that compounds gave significant co-relation.     

A new stereoselective synthesis of sterically constrained uncommon α,α′-dialkylated α-amino acids. Part 2

The alkylation of the diastereomeric mixture of the chiral morpholinone derivatives 5 and 6 occurs with good yield and a prevalence of the cis isomer. Cleavage of the alkylated intermediates 7b,c yields enantiomerically pure sterically constrained uncommon α,α′-dialkylated α-amino acids. The absolute configuration of the new stereocentres has been assigned on the basis of the ¹H NMR spectra and NOE measurements. A model to explain the observed diastereoselection is proposed.     

Iodine catalyzed one-pot multi-component reaction to CF3-containing spiro[indene-2,3′-piperidine] derivatives

In the presence of a catalytic amount of molecular iodine (0.1 equiv.), the one-pot multi-component reaction of ethyl trifluoroacetoacetate 1, indan-1,3-dione 2, ammonium acetate 3 and aromatic aldehyde 4 mainly gave the ethyl-6′-hydroxy-1,3-dioxo-2′,4′-diaryl-6′-(trifluoromethyl)-1,3-dihydrospiro[indene-2,3′-piperidine]-5′-carboxylate derivatives 5, along with the minor product 2-trifluoromethyl-2,3,4,5-tetrahydro-1H-indeno[1,2-b]pyridine derivatives 6. A plausible reaction mechanism for the formation of 5, 6 was presented. The structures of compounds 5, 6 were fully confirmed by ¹H NMR, ¹⁹F NMR, MS, IR spectroscopies and elemental analysis or high resolution mass spectra (HRMS). Meanwhile, the representative 5a and 6h were further confirmed by XRD analysis.     

Two new guaianolide-type sesquiterpenoids from Kadsura interior

Two new guaianolide-type sesquiterpenoids,4β,9β-dihydroxy-1α,5α-H-guaia-6,10(14)-dien(1) and 4β,9β,10α-trihydroxy-1α,5α-H-guaia-6-en(2),along with four known sesquiterpenoids(3a,3b,4 and 5),were isolated from Kadsura interior.Their structures and configurations were elucidated by spectroscopic methods including 2D-NMR and HR-MS techniques.Compounds 3a and 3b were obtained as a pair of enantiomers,and their structure and absolute configuration were established from their extensive NMR spectra and by single-crystal X-ray analysis.     

Synthesis and characterization of a new pillar[5]arene-based [1]rotaxane

In this study, we reported the synthesis of three kinds of mono-functional pillar[5]arene derivatives PRI, PRII and R and their structures were studied by 1D and 2D NMR spectra and mass spectra. The 2D NMR spectra including ¹H-¹³C HSQC, ¹H-¹H COSY and NOESY spectra indicated that PRI and PRII are both stable self-included pseudo[1]rotaxanes in CDCl₃. These original structures are promising compounds for the design of pillar[5]-based [1]rotaxane. And the results showed that R could exist stable in CDCl₃ and DMSO because of the coordination of N-H?O hydrogen bonding interaction and C-H?π interaction.