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The Reformatsky reaction of (3R,4R)-4-acetoxy-3-((1R)-1-{[tert-butyl(dimethyl)silyl]oxy}ethyl)­azetidin-2-one with ethyl 4-bromo-3-oxopentanoate gave product of replacement of the acetoxy group by C2-carbanion of the β-keto ester, which underwent retro-aza-Michael reaction with opening of the azetidinone ring with the formation of acyclic ethyl (2Z,4S,5R)-4-carbamoyl-5-{[tert-butyl(dimethyl)silyl]oxy}-2-pro­panoyl­hex-2-enoate. Treatment of the latter with di-tert-butyl dicarbonate afforded hex-3-enoate and dihydro­pyridin-6-one derivatives.

Selenosugars are interesting targets of organic synthesis as they would possess potential biological activities. However, 4-selenotherofuranose derivatives, which have trans configuration for the two dihydroxy substituents at the 2,3-positions and a glycoside bond at the anomeric position, are not available in the current selenosugar library. In this study, racemic 4-selenothreofuranose derivatives were synthesized from trans-3,4-dioxygenated tetrahydroselenophenes in 77-99% yields with the α/β selectivity about 7:3 via oxidation and subsequent seleno-Pummerer rearrangement. The acetoxy group introduced at the anomeric position was then substituted with various nucleophiles, including activated 6-chloropurine, which afforded 4'-selenothreonucleoside derivatives, in the presence of BF3·OEt2 or TMSOTf. The stereochemistry of the selenosugar products was established by 1H NMR spectroscopy as well as X-ray analysis. The similar α/β selectivity observed in the latter glycosylation reaction to that in the former seleno-Pummerer rearrangement suggested the mediation of a common selenonium intermediate (-Se+=C

A resorcinarene-based hemicarcerand, which consists of two cavitands covalently linked to each other by four alkyl chains, allows structural expansion and contraction by demetalation and metalation of Cu(I) cations with a size change of approximately 12 A. This metal-mediated switching of the two states regulates the conformations of acetoxy group-terminated alkyl chains. A guest binding study reveals the encapsulation of heptyl to undecyl chains in metal-free and Cu(I)-coordinated capsules. The chemical shifts of the acetoxy groups of the bound guests are the same in the metal-free capsule, while those in the Cu(I)-coordinated one differ from each other. This indicates that the metal-free capsule regulates its size to the bound guests, while the bound guests adopt their conformations to the cavity of the Cu(I)-coordinated capsules. 1H NMR measurements and molecular mechanics calculations suggest that the bound guests have extended conformations in the metal-free capsule, while the Cu(I)-coordinated capsule forces the bound guests to adopt folded conformations. The presence of folded conformations is supported by the conformational study with structurally similar capsules and a nonsymmetric guest, allowing us to observe nuclear Overhauser effects stemming from the folded conformations of the guest in the cavity.

The aim of this research paper was the preparation of aluminum chloride bonded to silica gel catalyst and its application in the modification of steroidal molecules. Steroidal oxazolidinethiones were prepared using silica-supported aluminum chloride (SiO2-AlCl3) under Microwave irradiation, which is common in organic synthesis to achieve high yields in shorter reaction times. The advantage of this method is that the usual procedure can be carried out without tiring and without a secondary product at the end of the reaction. Physicochemical techniques were used to identify the chemical structure of the prepared oxazolidinethiones. A rationalization of the conversion pathways from steroidal epoxides to oxazolidinethiones is sketched on the basis of current and previous results. Antioxidant activities i.e. DPPH assay, total antioxidant capacity and total reductive capability were performed for steroidal compounds, including reactants, and the results indicated that steroidal oxazolidinethione with acetoxy group had a promising activity among the tested steroids. In correlation with antioxidant activity, a promising steroid derivative was subjected to a molecular docking study for binding to tyrosine kinases, the target protein and showed a negative binding energy −7.8 Kcal/mol suggesting good affinity to the active pocket and can be considered as a better antioxidant in the biological system.

Palladium-catalyzed remote arylative substitution was achieved for the reaction of arylboronic acids with alkenes possessing a distant acetoxy group to provide arylation products having an alkene moiety at the remote position. The use of β-acetoxy elimination as a key step in the catalytic cycle allowed for regioselective formation of unstabilized alkenes after chain walking. This reaction was applicable to various arylboronic acids as well as alkene substrates.

New norbornene-based functional multiblock copolymers containing ethylene–vinyl acetate/vinyl alcohol sequences are synthesized via the olefin cross-metathesis reaction of polynorbornene with poly(5-acetoxy-1-octenylene) followed by CC bond hydrogenation and acetoxy group deprotection. Macromolecular cross-metathesis, a recently developed type of interchange reaction, was carried out in the presence of Grubbs’ ruthenium catalysts and monitored by in situ1H NMR and ex situ13C NMR spectroscopy. This results in copolymer formation and its gradual randomization by segment reshuffling promoted by polymer-based Ru-carbenes. The kinetic study reveals that, despite the presence of bulky acetoxy substituents in polyoctenamer chains, Grubbs’ catalyst interacts with them more easily than with polynorbornene chains, which have cyclopentane rings in the backbone. The rate of the subsequent interchange reaction is controlled by the interaction of [Ru]-poly(5-acetoxy-1-octenylene) carbenes with norbornene units. It is found that the acetoxy groups markedly slow down the interaction of [Ru]-polynorbornene carbenes with the CC bonds in octenamer units. Since these carbenes are relatively unstable, they cause a noticeable decay of the reaction active centers. Our study demonstrates that the chain structure and, therefore, physico-chemical characteristics of multiblock copolymers can be tailored by adjusting the cross-metathesis conditions, such as the polymer concentration, polymer to catalyst ratio, and reaction time. Polymer-analogous reactions of hydrogenation and deacetylation transform octenamer units into ethylene–vinyl acetate/vinyl alcohol segments and thus open up more possibilities for tuning the thermal, gas barrier, and hydrophobic/hydrophilic properties of the synthesized norbornene-based multiblock copolymers.

Here, we have described the design, preparation and detailed characterization of a new acetoxy functionalized aluminium based metal-organic framework (MOF) called CAU-10-OCOCH3 (1) (CAU stands for Christian-Albrechts-University). The desolvated compound was employed for the detection of perborate in a pure aqueous environment. The presented MOF based perborate sensing probe (1) was synthesized by employing 5-acetoxyisophthalic acid and AlCl3·6H2O as the linker molecule and metal salt source, respectively, in DMF/H2O medium at 120 °C for 12 h. The material (1') showed a very selective fluorescent turn-on response towards perborate in aqueous medium with the coexistence of several competitive analytes. A dramatic increment (65 fold) in emission intensity of the probe was observed within 5 min of the addition of perborate. A chemo-selective reaction between perborate and the acetoxy functionality and subsequent hydrolysis of the acetoxy group to the hydroxy group is the main cause of the turn-on nature of detection. The material showed a detection limit of 1.19 μM. The probe was also applied for the recognition of perborate in several environmental water samples. The material is the first ever MOF based probe for selective detection of perborate.

Background: Antibiotics play an important role in the treatment of infections to the humans and at the same time, irrational, frequent prescription of higher antibiotics, change in gene composition of microorganisms are all the reasons behind the development and introduction of new antibiotics against different microorganisms. Objective: In this project, an attempt has been made to synthesize some derivatives of diazenyl containing phenyl styryl ketones and also their in vitro screening was conducted against Mycobacterium tuberculosis, Escherichia coli, Klebsiella pneumonia, Bacillus subtilis, Staphylococcus aureus, Aspergillus niger and Candida albicans. Methods: Ten molecules were synthesized which are diazenyl containing chalcones. 4- aminoacetophenone was diazotised and piperidine was coupled with the formed diazonium chloride. Further, the acetoxy group underwent Claisen-Schmidt condensation with differently substituted aldehydes to form the final compounds- the chalcones. The proposed chemical structures were confirmed by different spectroscopic techniques like FTIR, 1H NMR and Mass spectroscopy. TLC was used to know that the reactants were exhausted and the formation of the product occurred. Sharp melting point of the compounds concludes the purity. Results: The MIC of the compounds 3CP, 3DP, 3EP and 3GP is 20 times the MIC of the standard fluconazole drug against Aspergillus niger. The compound 3GP is as equipotent as the standard drug Pyrazinamide with MIC of 3.12 µg/ml against Mycobacterium tuberculosis. Conclusion: The results are quite promising which on further studies may lead to drug molecules against different microorganisms. Especially, 3EP can be considered as a broad spectrum agent due to its potent activity against different microorganisms like Staphylococcus aureus, Escherichia coli, Klebsiella pneumonia and Candida albicans.

We have investigated gas‐phase fragmentation reactions of protonated benzofuran neolignans (BNs) and dihydrobenzofuran neolignans (DBNs) by accurate‐mass electrospray ionization tandem and multiple‐stage (MSn) mass spectrometry combined with thermochemical data estimated by Computational Chemistry. Most of the protonated compounds fragment into product ions B ([M + H–MeOH]+), C ([B–MeOH]+), D ([C–CO]+), and E ([D–CO]+) upon collision‐induced dissociation (CID). However, we identified a series of diagnostic ions and associated them with specific structural features. In the case of compounds displaying an acetoxy group at C‐4, product ion C produces diagnostic ions K ([C–C2H2O]+), L ([K–CO]+), and P ([L–CO]+). Formation of product ions H ([D–H2O]+) and M ([H–CO]+) is associated with the hydroxyl group at C‐3 and C‐3′, whereas product ions N ([D–MeOH]+) and O ([N–MeOH]+) indicate a methoxyl group at the same positions. Finally, product ions F ([A–C2H2O]+), Q ([A–C3H6O2]+), I ([A–C6H6O]+), and J ([I–MeOH]+) for DBNs and product ion G ([B–C2H2O]+) for BNs diagnose a saturated bond between C‐7′ and C‐8′. We used these structure‐fragmentation relationships in combination with deuterium exchange experiments, MSn data, and Computational Chemistry to elucidate the gas‐phase fragmentation pathways of these compounds. These results could help to elucidate DBN and BN metabolites in in vivo and in vitro studies on the basis of electrospray ionization ESI‐CID‐MS/MS data only.

Homogeneous polyimide (PI)/silica nanohybrid films were prepared using acetoxy group functionalized PI and silsesquiazane (SSQZ) as a silica precursor. During the heat treatment at 250 °C in a nitrogen atmosphere, the SSQZ was converted to silica. At the same time, the acetoxy groups of PI were converted into hydroxyl groups and formed covalent bonds with silica to make the resulting hybrid film homogeneous. FE-SEM and AFM analysis showed no evidence of macro-phase separation. As a result, the hybrid films exhibited improved thermal and mechanical properties, including 5% weight loss temperature, residual amount at 1,000 °C, coefficient of thermal expansion, and pencil hardness. The optical properties of the films also improved with showing a similar optical transmittance and lower yellow index.

Fifteen new analogues of (−)-cleistenolide (1) with aromatic ester groups at the C-6 position were designed and synthesized by multistep sequences. Steglich esterification of δ-pyrone 10 with selected aromatic acids (benzoic, cinnamic, and 4-substituted cinnamic acids) gave the corresponding 6-O-acyl derivatives 11–15. An original method was developed for the selective conversion of the primary benzyloxy group into the corresponding acetoxy function, giving five new bioisosteres (16–20) for biological testing. Finally, the dibenzyl derivative 11 was converted to the corresponding diacetate 2 using the AcBr/Zn(OTf)2 reagent system. For the transformation of compounds 12–15 into the corresponding 4,7-diacetates (3–6), in addition to Zn(OTf)2, it was necessary to use FeCl3 as a co-catalyst. The cleistenolide analogues thus obtained were tested for their in vitro antitumour activity The majority of compounds showed higher potency compared to lead 1 toward five of six investigated human tumour cell lines, but were almost completely inactive in the culture of normal foetal fibroblasts (MRC-5). The most potent antiproliferative activity was shown by 4,7-di-O-benzyl derivatives 13 and 14, with IC50 values of 0.04 (HeLa) and 0.09 μM (Jurkat), respectively. Preliminary SAR analysis revealed some of the structural features important for the activity of this class of compounds. These are: the presence of unsubstituted cinnamate function at the C-6 position and the presence of an acetoxy group at the C-4 position.

In this study, a series of variously substituted 2,3-dihydroquinolin-4-imines (DQIs) were synthesized from N-substituted propargylanilines by copper(I)-catalyzed annulation. The approach adopted in this study under mild, effective conditions exhibited broad substrate tolerance, particularly for functional groups substituted on anilines. Most of the DQI derivatives synthesized under optimal conditions were obtained in good isolated yields of 63-88 %. 2,3-Dihydroquinolinimine thus obtained was easily converted to important structures like 2,3-dihydroquinolone and tetrahydrobenzodiazepin-5-one, confirming the importance of this strategy in constructing various heterocycles. Surprisingly, 2,3-dihydroquinolinimines thus obtained exhibited bright fluorescence with quantum yields up to 66 %. The density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations were performed for understanding the excited-state nature of DQI system. Accordingly, a tailored DQI derivative bearing methoxy group at C-6 position and acetoxy group at C-7 position was designed and synthesized to give emission at 559 nm with redshift compared to the 7-methoxy substituted DQI. A detailed study of DQI structures with their photophysical properties was performed with five control molecules and consequently demonstrated the uniqueness of the chemical structures of DQIs.

A novel retro-ene reaction via a [4.4.3]propellane intermediate containing a quaternary ammonium linkage was developed. The feature of this acetic anhydride mediated rearrangement includes the elimination of an acetoxy group at the C14 position and subsequent intramolecular nucleophilic addition of a nitrogen functional group to form an isolable ammonium salt intermediate. We clarified the reaction mechanism utilizing the deuterated derivative.

13C NMR spectroscopic studies were performed for carbonyl compounds having a hydroxyl group, a carboalkoxy group, an acetoxy group, or a carboxyl group in various solvents with different polarities for observation of their behaviors of 13C NMR chemical shifts of carbonyl carbons in solutions. It was found that the chemical shifts of the carbonyl carbons in 13C NMR have good correlation with the empirical parameter for solvent polarities, ETN, depending on the structures. Inter- or intramolecular hydrogen bonding and dipolar-dipolar interactions appear to play a key role in this observation.

Seven new saikosaponins ( 1 − 7 ), together with four known ones ( 8 − 11 ), were isolated from the roots of Bupleurum chinense . Their structures were elucidated by comprehensive spectroscopic analysis and chemical methods. All obtained saikosaponins were oleanane-type, except for compound 11 , which was the first lupane–type saikosaponin isolated from the genus Bupleurum . Compound 1 represented the first example of saikosaponins bearing a hydroxyl group at C-15, while compound 4 was a saikosaponin containing acetoxy group at C-23 rarely found in genus Bupleurum . Compounds 6 and 7, bearing an n -butoxy moiety at C-11, were confirmed to be artifacts by LC–MS experiment. All the isolates were evaluated for their inhibitory effects towards nitric oxide production induced by lipopolysaccharide in BV-2 microglial cells, and saikosaponins A ( 9 ) and D ( 10 ) exhibited the most potent activity, which were comparable to the positive control dexamethasone.

Chemoenzymatic synthesis and modification of well-defined macrolactonic sophorolipid (SLML) analogues via a series of successive regioselective de-esterification/transesterification reactions is investigated. Of the lipases screened, Candida antartica lipase- B (Novozyme-435) successfully deacylated the C-6′ acetoxy group of natural and peracylated SLMLs. Subsequent transesterification with acylating agents (esters of fatty acids) was successful only with the C-6′ deacetylated natural SLML providing an avenue to well-defined analogues of varying amphilicity. The macrolactonic motif was essential for enzymatic recognition of the sophorose rings of these complex glycolipids. In the absence of the lactonic motif, the peracylated sophorose rings are not deacylated, rather the carboxyl end of the non-lactonic forms that was preferentially transesterified. All macrolactonic derivatives were characterized by IR, 1H, 13C, 1H-1H and 1H-13C NMR spectroscopy, as well as HRMS where applicable.

Turmeric (Curcuma longa) has been known for its antibacterial activity because it contains active curcumin. Antibacterial activity can be amplified by reducing its polarity, one of the ways is by modifying –OH on the phenolic group of curcumin to an acetoxy group by acetylation. The curcuminoid compound was extracted and curcumin was separated by column chromatography. Curcumin was modified by acetylation with Ni/SiO2 and pyridine catalyst. The products were then separated by column chromatography and all compounds were characterized using thin layer chromatography, FTIR, and UV-Vis. All compounds were tested for Escherichia coli and Bacillus subtilis bacteria. The results showed that acetylation curcumin with pyridine was more effective at 94 % conversion of di-O-acetylcurcumin compared to acetylation with Ni/SiO2 catalyst which has 90 % conversion but still in a mixture of di-O-acetylcurcumin, mono-O-acetylcumin and curcumin residual. Di-O-acetylcurcumin showed the highest antibacterial activity against E. coli with inhibitory zone diameters at 2 mm while the mono-O-acethylcurcumin showed the highest antibacterial activity against B. subtilis with inhibitory zone diameters at 3 mm.

Time resolved FTIR difference spectroscopy (DS) has been used to study photosystem I (PSI) with the disubstituted 1,4-naphthoquinones acequinocyl (AcQ) and lapachol (Lpc) incorporated into the A1 binding site. AcQ is a 2-acetoxy-3-dodecyl-1,4-naphthoquinone, Lpc is a 2-hydroxy-3-(3-methyl-2-butenyl)-1,4-naphthoquinone. To assess whether the experimental spectra are specific to different orientations of the quinone and their substitutions ONIOM-type QM/MM vibrational frequency calculations were undertaken for various orientations of the pigments and side-chain conformations in the A1 binding site. Comparison of calculated and experimental spectra for the reduced species (semiquinone anion) suggests that the orientation for the naphthoquinone ring in the binding site and specific side-chain conformations can be identified based on the spectra. In native PSI phylloquinone (PhQ) in the A1 binding site binds with its phytyl chain ortho to the hydrogen bonded carbonyl group. This is not found to be the case for the hydrocarbon tail of AcQ, which is meta to the H-bonded carbonyl group. In contrast, Lpc in PSI binds with its hydrocarbon tail also ortho to the H-bonded carbonyl group. Furthermore, comparison of calculated and experimental spectra indicates which conformations the acetoxy group of AcQ and the hydroxy group of Lpc adopt in the A1 binding site.

The development of a cyclization reaction to access amino-1,3-oxazines under mild conditions is described. The synthesis was achieved using dehydrating reagents, such as phosphorus pentoxide and Burgess reagent. In particular, the cyclization with Burgess reagent proceeded under mild conditions and tolerated potentially labile functional groups, such as the acetoxy group, and therefore can be used to synthesize β-secretase (BACE1) inhibitors with a variety of amino-1,3-oxazine warheads.

Starting from (±)-3-acetoxyglutarimide, diastereoselective formal synthesis of indole alkaloids (±)-eburnamonine, (±)-eburnaminol, and (±)-vindeburnol have been demonstrated via a common intermediate (±)-1-hydroxy-12-tosyl-2,3,6,7,12,12b-hexahydroindolo[2,3- a ]quinolizin-4(1 H )-one in very good overall yields. The acetoxy group from (±)-3-acetoxyglutarimide was first used to induce the diastereoselectivity and also as a latent source of ketone carbonyl group. The ste­reo­selective eliminations, reductions, and intramolecular cyclizations were the involved key steps.

The total synthesis and evaluation of a key systematic series of vinblastines that incorporate the first deep-seated changes to the substituent at C4 are detailed. The synthetic approach features an expanded and redefined scope of a 1,3,4-oxadiazole [4 + 2]/[3 + 2] cycloaddition cascade in which electronically mismatched electron-deficient trisubstituted alkenes and unactivated trisubstituted alkenes were found to productively initiate the cycloaddition cascade with tethered electron-deficient 1,3,4-oxadiazoles. Such cycloaddition cascades were used to directly introduce altered C4 substituents, providing the basis for concise total syntheses of a series of C4 modified vindolines and their subsequent single-step incorporation into the corresponding synthetic vinblastines in routes as short as 8–12 steps. Evaluation of the synthetic vinblastines revealed a surprisingly large impact and role of the C4 substituent on activity even though it was previously not thought to intimately interact with the biological target tubulin. Only the introduction of a C4 methyl ester, a constitutional isomer of vinblastine in which the carbonyl carbon and ester oxygen of the C4 acetate are transposed, provided a synthetic vinblastine that matched the potency of the natural product. In contrast, even introduction of a C4 acetamide or N-methyl carboxamide, which incorporate single heavy atom exchanges (amide NH for ester oxygen) in vinblastine or the C4 methyl ester, provided compounds that were ≥10-fold less active than vinblastine. Other C4 acetate replacements, including a C4 amine, carboxylic acid, hydroxymethyl or acetoxymethyl group, led to even greater reductions in potency. Even replacement of the C4 acetoxy group or its equally active C4 methyl ester with an ethyl or isopropyl ester led to 10-fold or more reductions in activity. These remarkable trends in activity, which correlate with relative tubulin binding affinities, retrospectively may be ascribed to the role the substituent serves as a H-bond acceptor for α-tubulin Lys336 and Asn329 side chains at a site less tolerant of a H-bond donor, placing the methyl group of the C4 acetate or C4 methyl ester in a spatially restricted and well-defined hydrophobic half pocket created by a surrounding well-ordered loop. This remarkable impact of the C4 substituent, its stringency, and even the magnitude of its effect are extraordinary, and indicate that its presence was selected in Nature to enhance the effects of vinblastine and related natural products.

A tandem reaction of 4-(1-acetoxyallyl)-1-sulfonyl-1,2,3-triazole including formation of α-imino rhodium carbene, 1,2-migration of an acetoxy group and six electron electrocyclic ring closure was reported. The migration of the OAc group with excellent chemoselectivity was the crucial process, leading to the formation of 1,2-dihydropyridine specifically in up to 90% yield. Several transformations of the dihydropyridine product were also achieved illustrating the potential of the protocol in organic synthesis. Based on the observation of the intermediate, a plausible mechanism was proposed.

Reaction of ethyl 2-bromomethyl-5-(1,2,3-thiadiazol-4-yl)furan-3-carboxylate with nucleophiles of different nature was studied. It is shown that substitution of bromine with acetoxy group takes place under the action of sodium acetate in the acetic acid. Stronger bases, like phenolates, cause considerable decomposition of the labile furylthiadiazole fragment Decomposition can be avoided only when this reaction is carried out in the presence of a phase transfer catalyst under the conditions of the ion pair extraction,. In the reaction with sodium N,N-diethyl dithiocarbaminate the corresponding thioester is formed. Butanethiol and thiophenol are alkylated as potassium thiolates. In the last case S-alkylation proceeds exclusively. Reaction with excess 2-aminoethanol permits to prepare secondary amine, and the reactions with pyrrolidine, piperidine, and morpholine give the corresponding tertiary amines. Phosphorylation with triethyl phosphite under the conditions of Arbuzov reaction leads to the corresponding diethyl phosphonate. In all these transformations furylthiadiazole fragment is retained.

A catalytic enantioselective synthesis of the hexahydropyrrolo[3,2-c]quinoline core structure found in the Martinella alkaloids, martinelline and martinellic acid, is described. The synthesis is completed without the use of any chiral building blocks or chiral auxiliaries. The key steps in our synthesis constituted a Sp2-Sp3 Suzuki-Miyaura cross-coupling reaction between a triflate and an N-protected β-aminoethyl boron species to provide a 1,2-dihydroquinoline carrying a N-protected β-aminoethyl group in the 3-position, Sharpless asymmetric dihydroxylation of the 1,2-dihydroquinoline derived from the Suzuki-Miyaura cross-coupling reaction, and an acid promoted intramolecular diastereoselective amido cyclisation with the aid of a neighbouring acetoxy group to provide the tricyclic architecture of martinelline and martinellic acid. Our catalytic enantioselective synthesis provided the hexahydropyrrolo[3,2-c]quinoline core structure of the Martinella alkaloids in 75 % ee.

tert-Butyl esters are demonstrated to function as chain transfer agents (CTAs) in the cationic copolymerization of vinyl ether (VE) and oxirane via concurrent vinyl-addition and ring-opening mechanisms. In the copolymerization of isopropyl VE and isobutylene oxide (IBO), the IBO-derived propagating species reacts with tert-butyl acetate to generate a copolymer chain with an acetoxy group at the ω-end. This reaction liberates a tert-butyl cation; hence, a polymer chain with a tert-butyl group at the α-end is subsequently generated. Other tert-butyl esters also function as CTAs, and the substituent attached to the carbonyl group affects the chain transfer efficiency. In addition, ethyl acetate does not function as a CTA, which suggests the importance of the liberation of a tert-butyl cation for the chain transfer process. Chain transfer reactions by tert-butyl esters potentially occur reversibly through the reaction of the propagating cation with the ester group at the ω-end of another chain.

A new series of furofuran lignans containing catechol moiety were prepared from the reactions between lignans and a variety of phenolics. All 22 products obtained were evaluated against three different α-glucosidases (maltase, sucrase and Baker’s yeast glucosidase) and DPPH radical. Of furofuran lignans evaluated, β-14, having two catechol moieties and one acetoxy group, was the most potent inhibitor against Baker’s yeast, maltase, and sucrase with IC50 values of 5.3, 25.7, and 12.9 µM, respectively. Of interest, its inhibitory potency toward Baker’s yeast was 28 times greater than standard drug, acarbose and its DPPH radical scavenging (SC50 11.2 µM) was 130 times higher than commercial antioxidant BHT. Subsequent investigation on mechanism underlying the inhibitory effect of β-14 revealed that it blocked Baker’s yeast and sucrase functions by mixed-type inhibition while it exerted non-competitive inhibition toward maltase. Molecular dynamics simulation of the most potent furofuran lignans (4, α-8b, α-14, and β-14) with the homology rat intestinal maltase at the binding site revealed that the hydrogen bond interactions from catechol, acetoxy, and quinone moieties of furofuran lignans were the key interaction to bind tightly to α-glucosidase. The results indicated that β-14 possessed promising antidiabetic activity through simultaneously inhibiting α-glucosidases and free radicals.

We report herein the first examples of asymmetric oxidation of enol ether and ester substrates using iminium salt organocatalysis, affording moderate to excellent enantioselectivities of up to 98% ee for tetralone-derived substrates in the α-hydroxyketone products. A comprehensive density functional theory study was undertaken to interpret the competing diastereoisomeric transition states in this example in order to identify the origins of enantioselectivity. The calculations, performed at the B3LYP/6-31G(D) level of theory, gave good agreement with the experimental results, in terms of the magnitude of the effects under the specified reaction conditions, and in terms of the preferential formation of the ( R)-enantiomer. Just one of the 30 characterized transition states dominates the enantioselectivity, which is attributed to the adoption of an orientation relative to stereochemical features of the chiral controlling element that combines a CH-π interaction between a CH2 group in the substrate and one of the aromatic rings of the biaryl section of the chiral auxiliary with a good alignment of the acetoxy group with the other biaryl ring, and places the smallest substituent on the alkene (a hydrogen atom) in the most sterically hindered position.

The oxidative deamination of N-nitroso N-acetylneuraminic acid (NeuAc) derivatives is a useful reaction for the formation of 5-desamino-5-hydroxy NeuAc derivatives and their stereoisomers. We demonstrated previously that replacement of the classical nucleophile in these reactions, acetic acid, by phenols resulted in a novel double displacement process with substitution of the acetoxy group at the 4-position taking place in addition to that of the 5-acetamido group, for which we postulated a mechanism centered on the formation of a highly reactive vinyl diazonium ion. We now extend these studies to encompass the use of hydroxylamine-based systems and weakly basic amines as nucleophile. We find that the nature of the product depends significantly on the pKa of the nucleophile, with the more acidic species typically affording only substitution at the 5-position, while the less acidic species give mixtures of elimination products and disubstitution products. The use of aniline as nucleophile is of particular note as it affords a novel aziridine spanning positions 4- and 5- of the neuraminic acid skeleton.

Irradiation of Lumogen Red 305 (3) in ethyl acetate with intense blue LED light led to very slow bleaching, showing a high photochemical stability. However, irradiation in ethanol led to the formation of a low yield product in which one of the phenoxy groups is substituted by an acetoxy group, the oxidized form of an ethoxy group. This reaction product was only formed in the presence of blue light and oxygen. Adding a small amount of acetic acid to the solutions resulted in a much higher yield of the product, indicating a possible photo oxidation of ethanol to acetic acid during the process in this solvent. A similar dye (5) containing less phenoxy side groups than Lumogen Red 305 showed the same reaction although the product formed showed lower chemical stability. The photo-substitution of phenoxy groups by acetoxy groups is a new reaction. The results are used to discuss the structural effects on the stability of these type of fluorescent dyes under irradiation conditions, potential reaction mechanisms and the possibility of using the photochemical transformations for preparative purposes.

Herein, nickel-catalyzed decarbonylative C–F bond alkylation of aroyl fluorides with organoboron reagents is reported. Aroyl fluorides are more chemically stable than the corresponding aroyl chlorides and can be readily synthesized from the corresponding carboxylic acids. The fluoronickel intermediate formed via oxidative addition interacts with Lewis-acidic trialkylboranes, and the subsequent decarbonylative alkylation proceeds. This new synthetic methodology allows 1,2-bifunctionalization of aromatic carboxylic acids via palladium-catalyzed ortho-C–H arylation. In addition, an unprecedented 1,4-nickel migration on ortho-arylated aroyl fluorides was observed. As a demonstration of the synthetic utility of the present reaction, the sequential 1-alkyl-2-arylation of 3-hydroxy-2-naphthoic acid was accomplished via chemoselective alkylation at a fluorocarbonyl moiety and the subsequent C–O bond arylation at an acetoxy group.

Testosterone (T) plays a crucial role in prostate growth. In androgen-dependent tissues T is reduced to dihydrotestosterone (DHT) because of the presence of the 5α-reductase enzyme. This androgen is more active than T, since it has a higher affinity for the androgen receptor (AR). When this mechanism is altered, androgen-dependent diseases, including prostate cancer, could result. The aim of this study was to synthesize several 16-dehydropregnenolone acetate derivatives containing a triazole ring at C-21 and a linear or alicyclic ester moiety at C-3 of the steroidal skeleton. These steroids were designed as potential inhibitors of the activity of both types (1 and 2) of 5α-reductase. The cytotoxic activity of these compounds was also evaluated on a panel of PC-3, MCF7, and SK-LU-1 human cancer cell lines. The results from this study showed that with the exception of steroids 20-oxo-21-(1H-1,2,4-triazole-1-yl)pregna-5,16-dien-3β-yl-propionate and 20-oxo-21-(1H-1,2,4-triazole-1-yl)pregna-5,16-dien-3β-yl-pentanoate, the compounds exhibit a lower inhibitory activity for both isoenzymes of 5α-reductase than finasteride. Furthermore the 3β-hydroxy-21-(1H-1,2,4-triazole-1-yl)pregna-5,16-dien-20-one and 20-oxo-21-(1H-1,2,4-triazole-1-yl)pregna-5,16-dien-3β-yl-acetate derivatives display 80% cytotoxic activity on the SK-LU-1 cell line. These results also indicated that the triazole derivatives, which have a hydroxyl or acetoxy group at C-3, could have an anticancer effect, whereas the derivatives with a alicyclic ester group at C-3 do not show biological activity.

Leonurus japonics Houtt. (Lamiaceae) is an annual or biennial herbaceous plant widely distributed and cultivated in China. The dried herb is used in TCM for the treatment of various diseases, especially menstrual disturbances, dysmenorrhea, and amenorrhea. Recently, phytochemical studies on this plant have been reported. Our previous investigation on two plants of the family Lamiaceae resulted in the isolation of a number of new labdane-type diterpenes. In our continuing research on secondary metabolites from L. japonicus, five diterpenoids including two new and three known ones were isolated and identified. The new compounds (Fig. 1) were elucidated as 1-((2S)-2-(3-(furan-3yl)propanoyl)-2,6,6-trimethylcyclohexyl)-2-hydroxybutan1-one (1), and 1-((1S,3R,3aS)-3-(2-(furan-3-yl)ethyl)-3methoxy-3a,7,7-trimethyloctahydroisobenzo furan-1-yl)propan-1-one (2). The known compounds were identified as seco-labdane (3), 6b-hydroxy-15,16-epoxylabda-8,13(16), 14-trien-7-one (4), and leojaponin (5). The ethanol extract of the powdered herb of L. japonicus was first separated by macroporious resin (D101) and then repeatedly separated by silica gel column chromatography, Sephadex LH-20, and preparative HPLC to give compounds 1–5. Compound 1 was obtained as a colorless oil, [α] D + 36.3 (c 0.1, MeOH), and was established to have a molecular formula of C20H30O4 by HRESIMS ([M + H] + m/z 335.2178; calcd. 335.2222). The H, C NMR and DEPT data (Table 1) exhibited resonances for three tertiary methyl groups (δH 0.76, 0.87, 0.90; δC 29.3, 29.5, 25.6, respectively), two carbonyl groups (δC 215.7, 213.2), a monosubstituted furan (δH 7.33, 7.23, 6.25; δC 110.9, 123.8, 139.2, 142.8), five methylenes (δC 37.2, 34.2, 31.4, 26.7, 19.5, 19.1), two methines including one oxygenated (δH 3.58 s, 4.03 d J = 8.0 Hz; δC 53.8, 80.6), and two quaternary carbons (δC 34.5, 49.9). These spectroscopic data indicated 1 to be an 8,9-seco-labdane diterpenoid with a hydroxyl group (δH 3.44 s). The H NMR data of 1 were similar to those of the lagopsin F and 8,9-secohispanolone except for the absence of the resonances of an acetoxy group and a replacement of carbonyl with a hydroxyl group in lagopsin F. However, carefully analysis of the H-H COSY spectra, the cross peak between the two protons of methines (H-5 and H-7) was not observed, and correlation from H-7 to H2-8 (δH 1.30 m) was obviously detected. It suggested that the hydroxyl group was connected to C-7, rather than C-6 as lagopsin F. The proposed structure of 1 was further confirmed by the HMBC correlations between H3-20 and C-1/C-5/C-9/C-10; H3-18 and C-19/C4/C-5; H3-17 and C-7/C-8; H-16 and C-13/C-14/C-15; H15 and C-13/C-14/C-16; H-14 and C-13/C-15/C-16; H2-12 and C-9/C-11/C-13/C-14/C-16; H2-11 and C-9/C-12/C-13; H-8 and C-7/C-17; H-5 and C-1/C-3/C-4/ C-6/C-7/C-9/C10, and H-7 and C-5/C-6/C-8/C-17 (Fig. 2). However, the C-7 relative configuration could not be assigned. Therefore, the structure of 1 was identified as 1-((2S)-2-(3-(furan-3yl)propanoyl)-2,6,6-trimethylcyclo-hexyl)-2-hydroxybutan -1-one, and named secoleojaponol. Compound 1 has not been previously reported. Compound 2, a colorless oil, [α] D 3.6 (c 0.1, MeOH) was shown to have a formula of C21H32O4 by HRESIMS ([M + H] m/z 349.2020; calcd. 349.2015). The NMR data (Table 1) showed that compound 2 has three tertiary methyl groups (δH 0.75, 1.04, 1.12; δC 33.6, 22.2, 17.0, respectively) and a methoxy group (δH 3.35, s; δC 48.8) a propanoyl group [δH 1.08 (3H, t, J = 8.0 Hz), 2.65 (2H, q, J = 8.0 Hz ); δC 7.6

Aromatic diyne systems bearing one terminal propargylic acetate moiety and one tertiary propargylic alcohol subunit were converted in the presence of a gold catalyst. After an initial 1,2-migration of the acetoxy group at the terminal alkyne, a gold carbenoid is formed which is then transferred onto the internal alkyne of the propargylic alcohol. This combination enables the use of propargylic acetates as precursors for a gold-catalyzed pinacol-type rearrangement. In the final pinacol-like step the shift of an alkyl or aryl moiety onto an electrophilic gold carbenoid/cation terminates the reaction and 1-naphthyl ketones are obtained as products. If electron-rich aromatic backbones are used, a mechanistically interesting alternative pathway including a retro-Buchner reaction is opened.

Methyl 5-acetyl-2-furoate has been prepared via oxidation of 5-(1-hydroxyethyl)-2-furoate with the Jones reagent. In turn, the starting compound has been synthesized via sequential chloroethylation of ethyl 2-furoate, substitution of chlorine with acetoxy group, and methanolysis of the acetate in presence of sodium methylate. The vinylog 2-furoate has been obtained as the major product via acetylation of ethyl 3-(2-furyl)-acrylate with acetic anhydride in the presence of magnesium perchlorate.

A pedagogically useful discovery-based undergraduate organic chemistry lab experiment probing the chemo- and diastereoselectivity in the NaBH4 reduction of two chiral ketoesters (benzoin acetate and benzoin benzoate) has been developed. This experiment complements a previously described and highly popular discovery-based experiment that probes the stereoselectivity in the NaBH4 reduction of the chiral ketone (±)-benzoin. Using reactions described in standard textbooks, students convert (±)-benzoin to the ketoester derivatives (±)-benzoin acetate and (±)-benzoin benzoate. In contrast to benzoin that has a single reducible ketone functional group, the ketoester derivatives have two reducible functional groups. In addition, the structural modifications made to the hydroxyl group of the benzoin molecule lead to an increase in the effective steric bulk of the OH group of benzoin, affording a larger acetoxy group and an even larger benzoxy group. Using NMR spectroscopy, students probe not only the chemoselectiv...

Twenty acyclic monoterpenes with different functional groups (acetoxy, hydroxyl, carbonyl and carboxyl) bearing a variable number of carbon double bonds were assayed as repellent and larvicidal agents against the West Nile vector Culex pipiens. Seven of them were derivatives that were synthesized through either hydrogenation or oxidation procedures. All repellent compounds were tested at the dose of 1mgcm(-2) and only neral and geranial were also tested at a 4-fold lower dose (0.25mgcm(-2)). Repellency results revealed that geranial, neral, nerol, citronellol, geranyl acetate and three more derivatives dihydrolinalool (3), dihydrocitronellol (5) and dihydrocitronellyl acetate (6) resulted in no landings. Based on the LC50 values the derivative dihydrocitronellyl acetate (6) was the most active of all, resulting in an LC50 value of 17.9mgL(-1). Linalyl acetate, citronellyl acetate, neryl acetate, geranyl acetate, dihydrocitronellol (5), dihydrocitronellal (7), citronellol, dihydrolinalyl acetate (2), citronellic acid and tetrahydrolinalyl acetate (1) were also toxic with LC50 values ranging from 23 to 45mgL(-1). Factors modulating toxicity have been identified, thus providing information on structural requirements for the selected acyclic monoterpenes. The acetoxy group enhanced toxicity, without being significantly affected by the unsaturation degree. Within esters, reduction of the vinyl group appears to decrease potency. Presence of a hydroxyl or carbonyl group resulted in increased activity but only in correlation to saturation degree. Branched alcohols proved ineffective compared to the corresponding linear isomers. Finally, as it concerns acids, data do not allow generalizations or correlations to be made.

The Hammett para constant ( σ p ) of the acetoxy group has been estimated by applying widely available quantum chemical descriptors, such as NPA charges, Wiberg bond indices, electron densities at bond critical points, as well as electrostatic potential at nuclei. The revised σ p value is predicted to be in the range of [−0.08, −0.02]. Direct evaluation of proton transfer free energies between the substituted benzoic acids and the benzoate anion by employing the SMD solvation model resulted in a reasonable linear correlation with the Hammett constants with a prediction of σ p = −0.02 for the OAc group.

The living cationic polymerization of 6-tert-butoxy-2-vinylnaphthalene (tBOVN), a vinylnaphthalene derivative with an electron-donating group, was achieved with a TiCl4/SnCl4 combined initiating system in the presence of ethyl acetate as an added base at –30 °C. The absence of side reactions at low temperature was confirmed by 1H NMR analysis of the resulting polymer. In contrast to this controlled reaction at –30 °C, reactions performed at higher temperature, such as 0 °C, frequently involved unwanted intramolecular or intermolecular Friedel–Crafts reactions of naphthalene rings due to the high electron density of these rings. The cationic polymerization of 6-acetoxy-2-vinylnaphthalene, a derivative with an acetoxy group, was also controlled under similar conditions, but chain transfer reactions were not completely suppressed during the polymerization of 2-vinylnaphthalene. The glass transition temperature (Tg) of the obtained poly(tBOVN) was 157 °C, a value higher by 94 °C than that of the corresponding styrene derivative. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4828–4834

RATIONALE Dimeric sesquiterpene lactones (DSLs) exhibit more 'biological friendly' and 'drug-like' molecular features than their monomers. Identification of DSLs is important to uncover potential lead compounds for the development of new anti-inflammatory and anticancer drugs. METHODS High-performance liquid chromatography coupled with electrospray mass spectrometry (HPLC/ESI-MS(n) ) in positive-ion mode was developed to analyze structurally related groups of DSLs in the species of Inula japonica Thunb. The aerial part of I. japonica was also analyzed by using HPLC-diode-array detection (DAD)/ESI-MS(n) for the purpose of method validation. RESULTS In positive-ion mode, a wealth of precursor molecular ions and product ions was detected for 24 DSL standards by MS(n) analysis under collision-induced dissociation. Retro-Diels-Alder (RDA) cleavage of the guaiane-type SL, neutral losses of acetoxy group, CO2 and water during the MS(n) process yielded characteristic product ions. The chemical constituents of the crude extract of I. japonica have also been analyzed by the developed method. CONCLUSIONS The results indicated that the developed analytical method could be employed as a rapid, effective technique for structural characterizations of DSL-type constituents in I. japonica. This study may also arouse interest for further structural analysis of other DSL-containing type herbal medicines.