Heck-type 5-endo-trig cyclizations promoted by vinylic fluorines: Ring-fluorinated indene and 3H-pyrrole syntheses from 1,1-difluoro-1-alkenes

Arylpalladium or aminopalladium species bearing a 2,2-difluorovinyl group undergo an unusual 5-endo alkene insertion followed by β-fluorine elimination. These processes provide a facile access to ring-fluorinated five-membered carbocyclic and heterocyclic compounds starting from an o-(3,3-difluoroallyl)phenyl trifluoromethanesulfonate and 3,3-difluoroallyl ketone O-pentafluorobenzoyloximes. In both systems, the two vinylic fluorine atoms are essential for Heck-type 5-endo-trig cyclizations.     

Unusual reaction of β-hydroxy α-diazo carbonyl compounds with TsNHNCHCOCl/Et3N

The reaction of β-hydroxy α-diazo carbonyl compounds with TsNHNCHCOCl/Et₃N gave β-(p-tolylsulfonyl) α,β-unsaturated carbonyl compounds or β-(p-tolylsulfonyl) α-diazo esters. The reaction mechanism is discussed.     

3-Thiolated 2-azetidinones: synthesis and in vitro antibacterial and antifungal activities

A series of 3-thiolated β-lactams were synthesized by [2+2] ketene-imine cycloaddition reaction from S-substituted mercaptoacetic acids and Schiff bases. Then, some of the 3-methylthio β-lactams were converted to 3-(methylsulfinyl) β-lactams and 3-(methylsulfonyl) β-lactams using m-CPBA under different reaction conditions. All the compounds were characterized by spectral data and elemental analyses and were evaluated for their in vitro antibacterial and antifungal activities against pathogenic strains including Staphylococcus aureus (Methicillin resistant strain). The preliminary screening results indicated that some of these compounds demonstrated moderate to very good antibacterial and antifungal activities.     

Catalyst-free Mannich-type reaction of 1-(N-acylamino)alkyltriphenylphosphonium salts with silyl enolates

A catalyst-free reaction of 1-(N-acylamino)alkyltriphenylphosphonium tetrafluoroborates with silyl enolates was developed to prepare β-amino carbonyl compounds. The reported method is a useful approach for the preparation of N-protected β-amino esters as well as N-protected β-amino ketones. The starting 1-(N-acylamino)alkyltriphenylphosphonium tetrafluoroborates are readily available from N-protected α-amino acids. Therefore, the presented approach can be considered a new method for the α-homologation of N-protected α-amino acids to prepare β-amino acid derivatives.     

New types of glycoconjugates: O-glycosylated, N-glycosylated and O-,N-diglycosylated isoserine derivatives

Starting from hexafluoroacetone-protected malic acid O-glycosylated, N-glycosylated and O-,N-diglycosylated (S)-isoserine derivatives have been synthesized. The new compounds represent glycosylated β-alanine surrogates, i.a. suitable for β-peptide modification.     

Synthesis of (E)-2-(1-ferrocenylmethylidene)malonic acid derivatives by a cobalt-catalyzed domino reaction of ethyl diazoacetate, carbon monoxide and ferrocenylimines

The domino reaction of ethyl diazoacetate, carbon monoxide and ferrocenylimines was investigated in the presence of Co₂(CO)₈ as catalyst. In most cases the main products are 2-(1-ferrocenylmethylidene) malonates formed by an N(1)-C(4) cleavage of the primarily derived β-lactams. The latter compounds could only be isolated when the reaction was carried out at relatively low CO pressure, using an excess of ethyl diazoacetate. trans-N-(tert-Butyl)-3-ethoxycarbonyl-4-ferrocenyl-β-lactam proved to be the most stable one among these compounds and could be isolated in 55% yield. N-alkyl β-lactams were shown to undergo acidic cleavage leading to the E isomers of 2-(1-ferrocenylmethylidene) malonates as the main products. The structures of the two new compounds, (E)-2-ethoxycarbonyl-3-ferrocenyl-N-((R)-1-phenylethyl)-2-propenamide and trans-N-(tert-butyl)-3-ethoxycarbonyl-4-ferrocenyl-β-lactam were confirmed by X-ray crystallography. The relative thermodynamical stability of the products as well as the energetics of the acid-mediated cleavage of the β-lactam ring was elucidated with DFT calculations.     

Synthesis of chiral vinylic sulfoxides by Pd-catalyzed asymmetric sulfinylzincation

Novel asymmetric sulfinylzincation of alkynoates has been accomplished via a Pd-catalyzed sulfinylzincation using 1-alkynyl sulfoxides bearing chiral auxiliaries as a sulfinylating reagent. The reaction proceeded in a highly syn-selective fashion, giving the (E)-β-sulfinyl α,β-unsaturated ester exclusively. Among the chiral sulfinylating reagents tested, an isoborneol-type compound (Rs)-4 showed the best results in terms of both yield and diastereoselectivity. As a result of optimization of the reaction, the selectivity was improved up to 92:8 dr, and stereochemistry of the newly formed sulfur stereogenic center was revealed as (Ss)-configuration.     

Formation of water-soluble vitamin derivatives from lipophilic vitamins by cultured plant cells

Glycosylation of vitamin E, its homologues, and vitamin A by cultured plant cells of Phytolacca americana and Catharanthus roseus was investigated to produce water-soluble vitamin derivatives. Two new compounds, that is, 2,5,7,8-tetramethyl-2-(4-methylpentyl)chroman-6-yl β-d-glucopyranoside and 2,5,7,8-tetramethyl-2-(4,8-dimethylnonyl)chroman-6-yl β-d-glucopyranoside, together with 2,5,7,8-tetramethyl-2-(4,8,12-trimethyltridecyl)chroman-6-yl β-d-glucopyranoside were isolated from the cultured cells of P. americana following administration of vitamin E and its homologues, that is, 2,5,7,8-tetramethyl-2-(4-methylpentyl)-6-chromanol, 2,5,7,8-tetramethyl-2-(4,8-dimethylnonyl)-6-chromanol and 2,5,7,8-tetramethyl-2-(4,8,12-trimethyltridecyl)-6-chromanol (vitamin E). On the other hand, glycosylation by C. roseus gave two new compounds, that is, 2,5,7,8-tetramethyl-2-(4-methylpentyl)chroman-6-yl 6-O-β-d-glucopyranosyl-β-d-glucopyranoside and 2,5,7,8-tetramethyl-2-(4,8-dimethylnonyl)chroman-6-yl 6-O-β-d-glucopyranosyl-β-d-glucopyranoside, as well. Furthermore, conversion of vitamin A (retinol) by these cultured cells afforded retinyl β-d-glucopyranoside.     

Porphins and their derivatives: XXIV. meso-Tetraphenylporphyrins with β-pyrazole rings

A series of 5-substituted 2-(2-phenyl-3,4-dihydro-2H-pyrazol-3-yl)porphyrins was prepared by treating with phenylhydrazine tetraphenylporphyrin derivatives containing in the β-position fragments of β-unsaturated ketones or aldehydes. The compounds obtained were oxidized with o-chloranil into the corresponding pyrazolylporphyrins.     

Novel reaction systems for the synthesis of O-glucosides by enzymatic reverse hydrolysis

Our studies are presented to replace alcohols as solvents in reverse hydrolytic reactions catalyzed by immobilized β-glucosidase to synthesize O-substituted β-d-glucopyranosides in preparative-scale. We found that 1,2-diacetoxyethane is a suitable solvent and O-alkyl or aryl β-d-glucosides were synthesized in moderate yields (after isolation 12-19%). In these reactions proportion of glucose and glucosyl acceptor hydroxy compounds was 1:20. We suggest that 1,2-diacetoxyethane can be useful not only for alcohols but for other glucosyl donor compounds unsuitable for the role of solvent (e.g., phenols) in the synthesis of O-β-d-glucosides by reverse hydrolysis.     

Stereoselective routes to substituted β-amino carbonyl compounds via heterodiene [4π+2π] cycloadditions of auxiliary-based C2 symmetric ketene acetals

Heterodiene [4π+2π] cycloadditions of (S,S)-4,5-diaryl-2-methylene-1,3-dioxolanes 1 to a series of β-amido-α,β-unsaturated carbonyl compounds are diastereoselective (d.r.≥4:1). The products can be purified by trituration or crystallisation and hydrolysed with acid to generate the corresponding β-amido carbonyl compounds, the overall sequence effecting an auxiliary-based enantioselective conjugate addition of an acetate enolate, leading to β-aminoacid derivatives.     

GC–MS Analysis of the Essential Oils of Piper nigrum L. and Piper longum L.

A simple, rapid and solvent-free method based on gas chromatography–mass spectrometry (GC–MS) following microwave distillation and headspace solid-phase microextraction (MD–HS-SPME) was developed for the analysis of the essential oils in two traditional Chinese medicines, Piper nigrum L. and Piper longum L. Thirty compounds were separated and identified from P. nigrum L. The main components were β-caryophyllene (23.49%), 3-carene (22.20%), d-limonene (18.68%), β-pinene (8.92%) and α-pinene (4.03 %). Forty-five compounds were separated from P. longum L. and identified. The main components were β-caryophyllene (33.44%), 3-carene (7.58%), eugenol (7.39%), d-limonene (6.70%), zingiberene (6.68%) and cubenol (3.64%). To demonstrate its advantages, MD–HS-SPME was compared to conventional HS-SPME. With conventional HS-SPME, only 28 and 33 compounds were detected in P. nigrum L. and P. longum L, respectively. Relative standard deviation (RSD) values of MD–HS-SPME for the essential oils in P. nigrum L. under optimal conditions were less than 10%. The results show that microwave distillation has a high extract efficiency and good precision and can be used to compare similarities and differences of essential oils.     

Crystal chemistry,magnetic, and electrical properties of hexagonal plutonium oxide chalcogenides: Pu2O2X, X = O,S, Se

A study was made of the influence of the chalcogen X on the magnetic and electrical properties of Pu₂O₂X (X = O, S, Se) compounds and on bonding in these hexagonal compounds, isostructural with the corresponding rare-earth compounds. The comparison of the cell volumes of Nd₂O₂X and Pu₂O₂X compounds showed that the Pu³⁺ crystal radius decreased from β-Pu₂O₃ to Pu₂O₂Se as “5f delocalization” and 5f-p overlap increased. These plutonium compounds were all found to be antiferromagnetic. This was caused by superexchange coupling interactions via p orbitals of the oxygen and chalcogen ions. The Néel temperature increased from β-Pu₂O₃ (26 K) to Pu₂O₂S (28 K) then to Pu₂O₂Se (34 K) showing that 5f-p covalency was enhanced as the chalcogen electronegativity decreased and the p radial extent increased. The hexagonal β-Pu₂O₃ was found to be an insulator while both other compounds were semiconductors with gaps around 0.5 eV. These gaps were interpreted as the energy separation between the 6d-7s conduction band and the np band of the chalcogen X with some overlap of the occupied 5f states and the np band. A simple electron band scheme of these compounds is proposed on such assumptions.     

Palladium-catalyzed arylation of vinylic acetates. Phosphine ligand influenced regioselectivity

A palladium-catalyzed coupling reaction of aryl bromides with vinylic acetates in the presence of tributyltin methoxide has been described. The α-arylation aldehyde product and the aryl ketone were obtained in the presence of P(t-Bu)₃ and P(o-Tol)₃, respectively.     

Enantioselective synthesis of 2-substituted-N-Boc-Δ-4,5-piperidines

The title compounds were prepared through a synthetic sequence involving: (i) a reaction of the condensation product between an enantiopure β-amino alcohol and an aldehyde with allylmagnesium chloride; (ii) an N-allylation of the resulting secondary amine; (iii) a chemoselective cleavage of the β-amino alcohol residue; and (iv) a protection of the secondary amine followed by a ring closing metathesis. The advantageous use of (1R,2S)-norephedrine was demonstrated in these syntheses.     

Bis-β-sulfanylethylester and cyclic disulfide-S-oxides as precursors of bifunctionalized anionic derivatives with two oxidized sulfurs

The cyclic disulfide and the bis-β-sulfanyl ethyl ester derived from dithiol, N,N′-1,2-phenylenebis(3-methyl-3-sulfanylbutanamide) were used as precursors to prepare upon oxidation the cyclic disulfide-S-oxides and the thioether sulfur oxidized species including thioether/sulfoxide, bis-sulfoxide, sulfoxide/sulfone, and bis-sulfone. Ring cleavage with KOH/EtOH of the cyclic disulfide-S-monooxide followed by reaction of the opened intermediate with ethyl acrylate afforded the sulfinate/β-sulfanyl ethyl ester derivative. Selective oxidation with 1 and 2 equiv of (3S)-3-tert-butyl-3-methyl-2-(phenylsulfonyl)oxaziridine or with 3 equiv of DMD led to the isolation of a series of compounds containing a sulfonate and a β-sulfanyl, a β-sulfinyl, and a β-sulfonyl ethyl ester. Retro-Michaël reaction applied to the β-sulfonyl/β-sulfinyl and bis-β-sulfonyl derivatives enabled to produce compounds containing a sulfinate and a β-sulfinyl or a β-sulfonyl ethyl ester as well as the bis-sulfinate dianion. DMD oxidation of the latter afforded the bis-sulfonate dianion. All these anionic species were characterized by ¹H NMR, mass spectrometry, HRMS or elemental analysis. Sulfenates in such pseudopeptidic structures could not be isolated from the ring cleavage of the cyclic disulfide-S-dioxide or from a retro-Michaël reaction applied to the β-sulfinyl ethyl ester. A cyclization reaction leading to an isothiazolidin-3-one is likely to occur as observed from the ring cleavage of the cyclic disulfide-S-dioxide. Finally, Ni(II) and Co(III) have been inserted into the disulfinate dianion leading to the corresponding diamidato/disulfinato complexes S-bonded to Ni(II) or Co(III) centers.     

H,C, Pt NMR study on platinum(II) interaction with sulphur containing Amadori compounds

The NMR study on the interaction of Pt(II) with Amadori compounds is performed. The Amadori compounds are derived from the reaction of β-d-glucose with l-cystine leading to N,N′-di-(1-deoxy-β-fructos-1-yl)-l-cystine [FruCyscys], and with l-methionine leading to N-(1-deoxy-β-fructos-1-yl)-l-methionine [FruMet].     

Isolation and TLC Densitometric Quantification of Gallicin, Gallic Acid, Lupeol and β-Sitosterol from Bergia suffruticosa, a Hitherto Unexplored Plant

Bergia suffruticosa (Elatinaceae family) is an important Indian medicinal plant hitherto unexplored for its chemical constituents and its pharmacological activity. In the present paper we report our work on isolation of gallicin, gallic acid, lupeol and β-sitosterol from the plant. To the best of our knowledge, this is the first report of these four compounds from this plant. Further, these four marker compounds were quantified by thin layer chromatography densitometric methods using high performance thin layer chromatography. The thin layer chromatography densitometric methods were found to be precise with RSD for intra-day in the range of 0.61–1.83, 1.14–1.57, 0.38–0.52 and 0.15–0.52 and for inter-day in the range of 0.97–1.45, 0.58–1.27, 0.42–0.50 and 0.26–0.61 for different concentrations of gallicin, gallic acid, lupeol and β-sitosterol. Instrumental precision was 1.05, 1.20, 0.65 and 0.85 (% RSD) for gallicin, gallic acid, lupeol and β-sitosterol. Accuracy of the method was checked by conducting recovery studies at three different levels for the four compounds and the average percentage recoveries obtained were 99.89, 100.58, 99.79 and 100.11%. B. suffruticosa sample was found to contain 0.34% w/w of gallicin, 0.288% w/w of gallic acid, 0.064% w/w of lupeol and 0.034% w/w of β-sitosterol.     

β-Ferrocenyl-α,β-unsaturated phosphonates and sulfones

Ferrocene reacts with β-ketophosphonates and β-ketosulfones (or acetals of formylphosphonates and sulfones) in the presence of a strong acid (triflic or methanesulfonic) to afford β-ferrocenyl-α,β-unsaturated phosphonates and β-ferrocenyl-α,β-unsaturated sulfones in good yield. The (E)-stereochemistry of these compounds was confirmed by spectral and analytical data, as well as by X-ray diffraction.     

Friedel-crafts cyclisation—IV: Intramolecular vs intermolecular acylation with β-aryl derivatives of propionyl chloride in aromatic substrates

Studies on the aluminium chloride-catalysed behaviour of β-phenylpropionyl, β,β-diphenylpropionyl, and β,β,β-triphenylpropionyl chlorides in anisole and some other aromatic stubstrates under standardised conditions are discussed. β,β-Diphenylpropionyl chloride gave yields of up to 27% 3-phenylindan-1-one in anisole and is one of the most easily cyclised acid chlorides so far reported. β,β,β-Triphenylpropionyl is less easily cyclised in anisole to 3,3-diphenylindan-1-one and its transformation product 2,3-diphenylind-1-one. The expected open-chain ketone is completely decomposed into products of αβ-ketonic cleavage and a subsequent redox reaction. Differences in ratios of intermolecular to intramolecular acylation (now called o/c ratios) are discussed.In benzene, β-bis-(p-chlorophenyl)propionyl chloride gave, in addition to the previously noted β-bis-(p-chlorophenyl)propiophenone (48%), the folloowing compounds: 6-chloro-3-(p-chlorophenyl)indan-1-one (4%) (the intramolecular acylation product), β-(p-chlorophenyl)-β-phenylpropiophenone (2·3%), ββ-diphenylpropiophenone (0·5%), 3-(p-chlorophenyl)-indan-1-one (5·2%). The transformation processes are discussed. Aluminium chloride-catalysed β-aryl exchange in acid chlorides is reported for the first time, but β-aryl exchange does not occur in ββ-(or 3,3-)di-aryl derivatives of indan-1-one.