Substrate-controlled diastereoselective aziridination of alkenes using 3-acetoxyaminoquinazolinone in the presence of hexamethyldisilazane

8-Phenylmenthol derived α,β-unsaturated esters were aziridinated highly diastereoselectively using 3-acetoxyamino-2-ethylquinazolinone. The yields of these aziridines were greatly improved in the presence of hexamethyldisilazane.     

Synthesis and structure elucidation of 25,26,27,28-tetramethylcalix[4]arene tetraketone using 1D and 2D NMR spectroscopies

The ¹H and ¹³C NMR spectra of the new calix[4]arene-based tetraketone were completely assigned by one- and two-dimensional homo- and heteronuclear experiments (¹H–¹H COSY, ¹H–¹³C HMQC, and HMBC) at 400 and 100 MHz, respectively, at 25 °C standard pulse sequence. ¹H and ¹³C spectra were measured at room temperature for 25,26,27,28-tetramethylcalix[4]arene tetraketone (1). ¹³C{¹H}, DEPT and NMR techniques were used to distinguish the methyl, methylene and methine carbon resonance signals of calix[4]arene 1. Correlation of 1D (¹H, ¹³C{¹H}, DEPT) and 2D (HMQC and HMBC) NMR data was used to completely assign various overlapping and broad signals of calix[4]arene 1. Heteronuclear multibond correlation (HMBC) studies were used to completely assign various carbon resonances. Our results show that the conformation of calix[4]arene 1 in the solution is very similar to the cone conformation reported in the literature.     

Synthesis and antifungal evaluation of 1-aryl-2-dimethyl- aminomethyl-2-propen-1-one hydrochlorides

The development of resistance to current antifungal therapeutics drives the search for new effective agents. The fact that several acetophenone-derived Mannich bases had shown remarkable antifungal activities in our previous studies led us to design and synthesize some acetophenone-derived Mannich bases, 1-8 and 2-acetylthiophene-derived Mannich base 9, 1-aryl-2-dimethylaminomethyl-2-propen-1-one hydrochloride, to evaluate their antifungal activities. The designed chemical structures have α,β-unsaturated ketone moieties, which are responsible for the bioactivities of the Mannich bases. The aryl part was C?H?(1); 4-CH?C?H? (2); 4-CH?OC?H? (3); 4-ClC?H? (4); 4-FC?H? (5); 4-BrC?H? (6); 4-HOC?H? (7); 4-NO?C?H? (8); and C?H?S(2-yl) (9). In this study the designed compounds were synthesized by the conventional heating method and also by the microwave irradiation method to compare these methods in terms of reaction times and yields to find an optimum synthetic method, which can be applied for the synthesis of Mannich bases in further studies. Since there are limited number of studies reporting the synthesis of Mannich bases by microwave irradiation, this study may also contribute to the general literature on Mannich bases. Compound 7 was reported for the first time. Antifungal activities of all compounds and synthesis of the compounds by microwave irradiation were also reported for the first time by this study. Fungi (15 species) were used for antifungal activity test. Amphotericin B was tested as an antifungal reference compound. In conclusion, compounds 1-6, and 9, which had more potent (2-16 times) antifungal activity than the reference compound amphotericin B against some fungi, can be model compounds for further studies to develop new antifungal agents. In addition, microwave irradiation can be considered to reduce reaction period, while the conventional method can still be considered to obtain compounds with higher reaction yields in the synthesis of new Mannich bases.     

Immobilization of growing cells by polyethyleneimine-modified alginate

A unique polymer matrix that is suitable for immobilizing growing cells has been developed. Alginate was chemically modified with polyethyleneimine (PEI), and the resultant polymer aggregate was evaluated as a cell carrier. Our method of immobilization depends on reversible gelation of the PEI-modified alginate. Our hypothesis is that immobilized cells grow by dissolving the surrounding gel matrix; the dissolved polymer adduct is displaced peripherally and gelled again by the influx of calcium ion from the surrounding fermentation broth, retaining both cells and carrier polymer in the gel beads. Thus, the immobilized cells gain space for growth by expanding the carrier matrix. The PEI modification offers the following advantages: (1) improved mechanical strength; (2) improved cell retention; (3) increased catalyst life; (4) ease of pelletization; and (5) an apparent bacteriostatic capability. When immobilized yeast cells were applied to a continuous ethanol fermentation, 94% theoretical conversion of glucose to ethanol was observed, with a reactor productivity of 15–30 g/L/h in a nonsterile reactor. A 3-mo catalyst life and minimal cell washout were observed.     

Cytotoxic naphthoquinones from Arnebia densiflora (Nordm.) Ledeb and determining new apoptosis inducers

Abstract

In this study, phytochemical composition of Arnebia densiflora (AD) was determined and cytotoxic effects of the n-hexane extract and compounds isolated from this species on various cell lines were investigated. By means of serial chromatographic studies, 6 naphthoquinone derivatives were yielded, which are isovalerylalkannin, α-methyl-n-butyl alkannin, acetylalkannin, β-acetoxy isovalerylalkannin, alkannin and a new compound: 4-hydroxy 4-methyl valeryl alkannin. Structures of the isolated compounds were elucidated using UV, IR, 1D-2D NMR, MS and CD methods. Cytotoxic effects of the extract and isolated alkannins were investigated on L929, HeLa, HEp-2 cells. AD and the isolated compounds demonstrated moderate to strong cytotoxic effects (IC₅₀ range: 4.92-172.35?µg/ml). The results of DNA fragmentation and caspase-3 activity studies on HeLa cells exhibited that AD and the naphthoquinones isolated from it caused cytotoxicity through induction of apoptosis.

     

β-Hydroxydihydrochalcone and flavonoid glycosides along with triterpene saponin and sesquiterpene from the herbs of Pimpinella rhodantha Boiss.

A new β-hydroxydihydrochalcone glycoside named ziganin (1) and a new acylated flavonol glycoside named isorhamnetin-3-O-α-L-(2″,3″-di-O-trans-coumaroyl)-rhamnopyranoside) (2), along with two known flavonoid glycosides, a β-hydroxydihydrochalcone glycoside, a hydroxybenzoic acid derivative, a trinorguaiane type sesquiterpenoid, a triterpenic saponin and a polyol were isolated from the herbs of Pimpinella rhodantha Boiss. Their structures were elucidated on the basis of spectroscopic analyses including 1D-and 2D-NMR, UV, IR, CD, ESI-MS, APCI-MS, HR-ESI-MS techniques. The isolated compounds were evaluated for their antioxidant capacity through the DPPH free-radical scavenging assay and ferrous ion-chelating power test.     

Synthesis, reactivity and biological activity of novel bisbenzofuran-2-yl-methanone derivatives

Preparation of bisbenzofuran-2-yl-methanone (1), the corresponding ketoxime 4, semicarbazone and thiosemicarbazone 3a and 3b, ether derivatives of the ketoximes 5a-j and the alcohol 2 are described. These substances have been prepared in excellent yields. All the synthesized compounds except 5i have been tested against five different microorganisms and some of them were found to be active against some of the species studied.     

Synthesis and structure elucidation of bromination products from dibromohomobenzonorbornadienes: high temperature bromination--part 17

The electrophilic addition of bromine to dibromohomobenzonorbornadiene derivatives at -45 +/- 5 degrees C led to the formation of the rearranged and non-rearranged tetrabromides in a ratio of 6:4. However, high-temperature bromination of the same system in CCl4 at 77 degrees C produced only non-rearranged products. The formation mechanism of the isomers and the role of the substituent on the rearrangement is discussed. The structure elucidation of the isomeric tetrabromides was achieved from NMR spectral data. The agreement between the calculated dihedral angles and the measured coupling constants is especially excellent. The gamma-gauche effect is discussed.     

A Concise Synthesis of 2‐Amino‐1,2,3,4‐tetrahydronaphthalene‐6,7‐diol (‘6,7‐ADTN’) from Naphthalene‐2,3‐diol

2‐Amino‐1,2,3,4‐tetrahydronaphthalene‐6,7‐diol ( 2 ; 6,7‐ADTN) was synthesized starting from naphthalene‐2,3‐diol in seven steps and with an overall yield of 44%. Methylation of naphthalene‐2,3‐diol with dimethyl sulfate, followed by Friedel? Crafts acylation with AcCl, gave 2‐acetyl‐6,7‐dimethoxynaphthalene. 2‐Acetyl‐6,7‐dimethoxynaphthalene was converted to 6,7‐dimethoxynaphthalene‐2‐carboxylic acid by a haloform reaction. Birch reduction of the carboxylic acid with 4 mol‐equiv. of Na in liquid ammonia afforded 1,2,3,4‐tetrahydro‐6,7‐dimethoxynaphthalene‐2‐carboxylic acid, from which 2 was obtained by a Curtius reaction, followed by hydrogenolysis and demethylation.     

Supramolecular inclusion complexes of a star polymer containing cholesterol end‐capped poly(ε‐caprolactone) arms with β‐cyclodextrin

A novel hexa‐armed and star‐shaped polymer containing cholesterol end‐capped poly(ε‐caprolactone) arms emanating from a phosphazene core (N₃P₃‐(PCL‐Chol)₆) was synthesized by a combination of ring‐opening polymerization and “click” chemistry techniques. For this purpose, the terminal ? OH groups of the synthesized precursor (N₃P₃‐(PCL‐OH)₆) were converted into –Chol through a series of reaction. Both N₃P₃‐(PCL‐OH)₆ and N₃P₃‐(PCL‐Chol)₆ were then employed in the preparation of supramolecular inclusion complexes (ICs) with β‐cyclodextrin (β‐CD). The latter formed ICs with β‐CD in higher yield. The host–guest stoichiometry (ε‐CL:β‐CD, mol:mol) in the ICs of N₃P₃‐(PCL‐Chol)₆ was found to be 1.2. The formation of supramolecular ICs of N₃P₃‐(PCL‐Chol)₆ with β‐CD was confirmed by using Fourier transform infrared (FTIR) and ¹H nuclear magnetic resonance (NMR) spectroscopic methods, wide‐angle X‐ray diffraction (WAXD), and thermal analysis techniques. WAXD data showed that the obtained ICs with N₃P₃‐(PCL‐Chol)₆ had a channel‐type crystalline structure, indicating the suppression of the original crystallization of N₃P₃‐(PCL‐Chol)₆ in β‐CD cavities. Moreover, the thermal stabilities of ICs were found to be higher than those of the free star polymer and β‐CD. Furthermore, the surface properties of N₃P₃‐(PCL‐Chol)₆ and its ICs with β‐CD were investigated by static contact angle measurements. The obtained results proved that the wettability of N₃P₃‐(PCL‐Chol)₆ successfully increased with the formation of its ICs with β‐CD. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 3406–3420