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 of haloconduritols from an endo-cycloadduct of furan and vinylene carbonate

A method for preparing haloconduritols having a conduritol-A construction is described. A mixture of endo- and exo-cycloadduct derivatives prepared from the Diels-Alder reaction of furan and vinylene carbonate was converted into diacetate derivatives by hydrolysis (K₂CO₃/MeOH) followed by acetylation (Ac₂O/pyridine). Boron trihalide (BBr₃ or BCl₃)-assisted ring-opening of the endo-diacetate in CH₂Cl₂ at −78°C gave (1α,2α,3β,6β)-6-halogeno-4-cyclohexene-1,2,3-triol 1,2-diacetate from which the corresponding triacetate was prepared by acetylation (AcCl). trans-Esterification of the triacetate (MeOH/HCl) afforded (1α,2α,3β,6β)-6-halogeno-4-cyclohexene-1,2,3-triol (X=Br or Cl). BF₃-Assisted ring-opening of the endo-diacetate in CH₂Cl₂ gave (1α,2α,3β,6β)-6-chloro-4-cyclohexene-1,2,3-triol 1,2-diacetate by means of halogen exchange.     

Addition of hypobromous acid to 1-phenylcycloalkenes

Reaction of 1-phenylcyclooctene and 1-phenylcycloheptene with N-bromosuccinimide (NBS) in aqueous DMSO gives the corresponding 3-bromo-2-phenylcycloalkenes and 2-phenylcycloalk-2-enols in a ratio of 3 : 1. Unlike them, 1-phenylcyclohexene gives a mixture of 3-bromo-2-phenylcyclohexene and 2-bromo-l-phenylcyclohexanol. The oxidation of allylic alcohols with pyridinium chlorochromate afforded the corresponding α,β-unsaturated ketones.     

Impact of sourcing flexibility on the outsourcing of services under demand uncertainty

This paper investigates the relationship between market conditions and the value and use of sourcing flexibility for service processes. We develop and analyze a series of models, and we derive expressions for the optimal switching decision, the value of the option to outsource, the value of the option to backsource, and the probability and timing of switches between the alternative sources.     

Synthesis of some bisnitrosaccharins

Method for synthesis of previously unknown bisnitrosaccharins from 6-nitrosaccharin under the action of bishalide compounds in polar aprotic solvents in the presence of anhydrous potassium carbonate is suggested.     

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.