Search

Two new meroterpenoids, aperterpenes N (1) and O (2), along with two known structurally related derivatives, terretonins A (3) and G (4), were isolated and identified from the marine algal-derived endophytic fungus Aspergillus terreus EN-539. Their structures and absolute configurations were determined by a detailed interpretation of spectroscopic data and by X-ray crystallographic analysis. This is the first establishment of the absolute configurations for terretonins A (3) and G (4). Compound 1 showed inhibitory activity against influenza neuraminidase (IC50 = 18.0 nM), and compound 4 showed inhibitory activity against Micrococcus luteus and Staphylococcus aureus, with MIC values of 32 and 8 μg/mL, respectively.

Aromatic secondary amines (Ar-SAs), constituted of several analogues with varied substitutions in molecular structure, are among the most frequently used anthropogenic antioxidants. Despite the reported toxicity effects, little information is available on their environmental contamination, except for few particular congeners such as diphenylamine. In this study, the occurrence of two kinds of Ar-SAs, substituted diphenylamines (S-DPAs) and novel substituted p-phenylenediamines (S-PPDs), was investigated in dust samples collected from outdoor rubber playgrounds and residential houses. Seven S-DPAs (GM: 102 ng/g) and two S-PPDs (GM: 20.9 ng/g) were detected in indoor dust. Significantly higher concentrations of S-DPAs (GM: 422 ng/g) and S-PPDs (GM: 31.6 ng/g) were observed in playground dust (p < 0.05). Different dominant Ar-SA congeners were found for indoor dust (low molecular weight Ar-SAs) and playground dust (high molecular weight Ar-SAs), indicating varied sources of Ar-SAs for different dust matrices. Apart from these parent chemicals, three diphenylamine derivatives, including N-nitrosodiphenylamine, 2-nitrodiphenylamine, and 4-nitrodiphenylamine, were also confirmed in indoor dust (GM: 35.7 ng/g) and playground dust (GM: 7.88 ng/g). A preliminary estimated daily intake calculation via dust ingestion indicated no immediate health risk to Chinese population. To our knowledge, this is the first report on the occurrence of a wide range of Ar-SAs and related derivates in dust matrices.

We evaluate the empirical validity of the compound option framework. In a model where corporate securities are options on a firm's assets, option contracts on these can be viewed as options on options, or compound options. We estimate a model with priced asset variance risk and find that it jointly explains the level and time variation of both equity index (SPX) and credit index (CDX) option prices well out-of-sample. This suggests that the two options markets are priced consistently, contrary to recent findings. We show that variance risk is important for establishing pricing consistency between equity, credit, and related derivatives.

This note explores a secondary effect of the GameStop short squeeze event and links the exalted focus of retail investors on meme stocks to financial literacy and autodidacticism. From an overview of stylized facts about the short squeeze of GameStop based on high frequency data, short interest, and key figures of related derivatives, it is shown that these financial concepts are reflected in keyword searches across multiple platforms. This self-education with regard to financial terms, keywords, and products and the understanding of basic market speculation mechanisms such as short sales plays a significant role for the influx of retail investors.

This note presents a preliminary approach to the design of an across-the-curve credit spread index (AXI). The index is a measure of the recent average cost of wholesale unsecured debt funding for publicly listed U.S. bank holding companies and their commercial banking subsidiaries. This may be a useful benchmark for bank lending and related derivatives risk management applications. The index is a weighted average of credit spreads for unsecured debt instruments with maturities ranging from overnight to five years, with weights that reflect both transactions volumes and issuance volumes. We provide preliminary illustrative output of the bond-based component of AXI using TRACE secondary-market price and volume data from 2002–2019. We have only extremely preliminary estimates of the short-maturity (money-market) spread component.

Fluorine chemistry has represented a hot topic in drug research over the last decade. Because of their pharmaceutical potential, fluorine-containing amino acids and related derivatives have acquired high importance among medicinal chemists. Therefore their synthesis and the development of various synthetic methods for these types of molecular scaffolds have gained increasing interest in synthetic organic chemistry. The current review focuses on synthetic protocols towards fluorine-containing amino acid derivatives through late-stage fluorination with various nucleophilic reagents, describing the access of various open-chain and cyclic α-, β-, γ-amino acid derivatives.

Recent advances in stem cell research and nanotechnology have significantly influenced the landscape of tissue engineering and regenerative medicine. Precise and reproducible control of the fate of stem cells and their lineage specification have, therefore, become more crucial than ever for the success of stem cell-based technologies. Extensive research has been geared towards developing materials that are capable of mimicking the physiological microenvironment of stem cells and at the same time, controlling their eventual fate. An interesting example of these materials is two-dimensional graphene and its related derivatives. A high specific surface area coupled with superior chemical stability, biocompatibility, and flexibility in functionalization render graphene-based nanomaterials one of the most exciting platforms for tissue engineering and regenerative medicine applications, especially for stem cell growth, proliferation, and differentiation. In this review, we discuss the love-hate relationship between stem cells and graphene-based nanomaterials in tissue engineering and regenerative medicine. We first discuss the role and importance of stem cells in tissue engineering and regenerative medicine. We then highlight the use of nanomaterials for stem cell control, the interaction between stem cells and graphene nanomaterials as well as their biocompatibility, biodistribution, and biodegradability considerations. We also offer our perspectives on the various challenges and opportunities facing the use of graphene and its derivatives for stem cell growth and differentiation.

Guanosine and related derivatives self-assemble in the presence of cations like potassium into supramolecular G-quadruplexes (SGQs), where four guanine moieties form planar tetrads (T) that coaxially stack into columnar aggregates with broad size distributions. However, SGQs made from 8-aryl-2’-deoxyguanosine derivatives (8ArGs), form mostly octamers, or two-tetrad (2T)-SGQs, while some form dodecamers (3T-SGQs), or hexadecamers (4T-SGQs), and none reported to date form higher assemblies. A theoretical model that addresses the configurational space available for the multiple pathways available for 8ArGs to self-assemble into SGQs is used to frame a series of molecular dynamics simulations (MDS) with selected SGQs. Some key insights from this work include: (a) The predicted entropic costs are not significantly higher for SGQs with more subunits due to their hierarchical assembly pathways; (b) The multiple isomeric SGQs vary in the interfacial contacts between consecutive tetrads, due to their two distinct sides (head, h; tail, t), with the MDS supporting the predicted order of stability of hh > ht > tt for octamers. (c) Such order also applies to dodecamers and hexadecamers, but with context-dependent exceptions due to strong allosteric effects. (d) The main factor disfavoring the tt interface is the repulsive dipolar interactions between the O4’ from ribose moieties on adjacent tetrads. (e) SGQs with 5 or more tetrads are disfavored because the attractive interactions are not large or strong enough to overcome the many repulsive forces resulting from the addition of further tetrads. We expect these findings provide some guidelines to enable the further development of SGQs into functional materials.

A new Bis-sesquiterpene, Nanji A ( 1 ), has been isolated together with 7 known compounds, debromolaurinterol ( 2 ), laurinterol ( 3 ), laurinterol acetate ( 4 ), isolaurinterol ( 5 ), 3α-hydroperoxy-3-epiaplysin ( 6 ), 3β-hydroperoxyaplysin ( 7) , Laurokomurenene A ( 8 ), from the Nanji red alga Laurencia okamurai . The structure of 1 was elucidated on the basis of extensive spectroscopic analysis of its EIMS, 1D and 2D NMR data. Furthermore, the chemotaxonomic significance of these compounds was also summarized.

Novel main group element compounds, geminal dianionic derivatives of the heavier group 14 elements; namely, 1,1-dilithiosilanes, 1,1-dilithiogermanes and 1,1-dilithiostannanes (and closely related derivatives of the cyclopentadiene-1,1-diide and cyclobutadiene dianion), are the focus of the present review. The synthetic strategies for their preparation, structural features, and synthetic applications are discussed.

The semi-syntheses of taraxerane triterpenoids by diverse bromination processes and other reactions, from oleanolic acid and some closely related derivatives, have been performed. For all the reactions performed, suitable mechanisms to explain the formation of these derivatives have been proposed.

This paper provides a complete-market valuation framework for emission allowances and related derivatives. In particular we present a structural model by assuming an emission rate with time-homogeneous parameters, where closed-form expressions are derived for allowances, allowance futures, and option prices. In addition, we also discuss the completeness of the allowance market and the source of incompleteness as supported by empirical evidence. While identifying limitations of the models, we present in detail their applications under information incompleteness, with a focus on deriving implied emission values from actual market data. Finally, the model is implemented using real world allowance data, based on which a comparative analysis is undertaken.

Hydrolytically sensitive polymers that degrade into benign products are of interest as biomedical materials. The aim of this study was to determine the properties and hydrolytic characteristics of both poly(diethoxyphosphazene) and related derivatives with both ethoxy and hydrophobic co-substituent groups in a near-1:1 M ratio such as 2,2,2-trifluoroethoxy, phenoxy, or p-methylphenoxy units. These hydrophobic cosubstituents served as models for bioactive counterparts. The hydrolytic sensitivity of the ethoxyphosphazene units was so pronounced that even hydrophobic or bulky O-linked co-substituents failed to counteract the hydrolysis behavior during a twelve-week hydrolysis study. This work illustrates a pathway for the development of a new class of useful bioerodible polymers.

Extant literature investigates volatility spillovers between spot markets of the same asset class or between derivatives and their underlying spot markets. This paper investigates economic spillovers between the freight and commodity derivatives markets. The economic relationship tested links the derivative price of the commodity transported with the derivative price on the freight rate. High frequency data on commodities are synchronised with freight data and freight rates of different vessels are matched with portfolios (baskets) of commodities that these vessels carry. The investigation of various types of commodities transported under different types of freight contracts reveal that in most cases new information appears first in the returns and volatilities of the commodities futures markets, before it is spilled over into the freight derivatives markets. Thus, agricultural commodity futures informationally lead the freight markets. The results can help improve the understanding of the information transmission mechanisms between freight and commodity markets.

By a scaffold elongation strategy, a series of ( Z )-3-(5-(3-benzyl-4-oxo-2-thioxothiazolidinylidene)methyl)- N -(3-carboxy-4-hydroxy)phenyl-2,5-dimethylpyrroles and related derivatives with a linear multi-aromatic-ring skeleton were designed, synthesized, and evaluated in HIV-1 gp41 and cellular assays. Among them, the most active compounds, 12e , 12g , and 12k with a one-carbon linker ( n = 1) between the rhodanine (C) and phenyl (D) rings, exhibited very promising inhibitory potency with IC 50 values of 1.8–2.6 μM and EC 50 values of 0.3–1.5 μM against gp41 6-HB formation and HIV-1 replication in MT-2 cells, respectively. Additionally, they were almost equally effective against both T20-sensitive and resistant strains. The related SAR studies and molecular modeling results provided potential for further developing a new class of non-peptide small molecular fusion inhibitors targeting the HIV-1 gp41.

Corticosteroids emerged in the late 1940s, at a time when steroid chemistry began to offer new therapeutic approaches. Extractive chemistry (T. Reichstein), chemical synthesis (E.C. Kendall) and clinical investigations (P. Hench) were combined to result in the discovery of cortisone in 1948, leading to a long series of related derivatives. Besides their first applications to treat Addison's disease and rheumatic or inflammatory diseases, corticosteroids could easily correct many metabolic and functional symptoms. Fluoridation of the steroid skeleton allowed the development of more active and better tolerated molecules. Corticosteroids have revolutionized the treatment of allergic diseases or immunity troubles, graft rejection, many dermatological, respiratory, digestive, eye diseases, etc. It is used today in all areas of therapeutic.

The synthesis of fluorinated highly modified nucleoside analogues—carbanucleosides, aromatic nucleosides, acyclic nucleosides and related derivatives are reviewed.

The hydrophilic polymer PEG and its related derivatives, have served as therapeutic agents to reconstruct the phospholipid bilayers of damaged cell membranes by erasing defects in the plasmalemma. The special attributes of hydrophilic polymers when in contact with cell membranes have been used for several decades since these well-known properties have been exploited in the manufacture of monoclonal antibodies. However, while traditional therapeutic efforts to combat traumatic injuries of the central nervous system (CNS) have not been successful, nanotechnology-based drug delivery has become a new emerging strategy with the additional promise of targeted membrane repair. As such, this potential use of nanotechnology provides new avenues for nanomedicine that uses nanoparticles themselves as the therapeutic agent in addition to their other functionalities. Here we will specifically address new advances in experimental treatment of Spinal Cord and Traumatic Brain injury (SCI and TBI respectively). We focus on the concept of repair of the neurolemma and axolemma in the acute stage of injury, with less emphasis on the worthwhile, and voluminous, issues concerning regenerative medicine/nanomedicine. It is not that the two are mutually exclusive - they are not. However, the survival of the neuron and the tissues of white matter are critical to any further success in what will likely be a multi-component therapy for TBI and SCI. This review includes a brief explanation of the characteristics of traumatic spinal cord injury SCI, the biological basis of the injuries, and the treatment opportunities of current polymer-based therapies. In particular, we update our own progress in such applications for CNS injuries with various suggestions and discussion, primarily nanocarrier-based drug delivery systems. The application of nanoparticles as drug-delivery vehicles to the CNS may likely be advantageous over existing molecular-based therapies. As a "proof-of-concept", we will discuss the recent investigations that have preferentially facilitated repair and functional recovery from breaches in neural membranes via rapid sealing and reassembly of the compromised site with silica or chitosan nanoparticles.

A series of N2-{2-[4-aryl(benzyl)-1-piperazinyl(piperidinyl)]ethyl}pyrrolo[3,4-d]pyridazinones 4 and related derivatives 5 were synthesized as potential analgesic agents. The structures of the new compounds were elucidated by micro, spectral and X-ray analysis. Analgesic activity of the compounds was investigated in the phenylbenzoquinone induced ‘writhing’ and ‘hot plate’ test in mice and at radioligand binding assay. At ‘writhing’ test all compounds, without exception, were more active than acetylsalicylic acid (ASA) with ED50 values ranging from 0.04 to 11 mg/kg (i.p.) (ED50 for ASA – 39.15 mg/kg). Analgesic effect at the ‘hot plate’ test was observed for three compounds 4c,e,f at the dose 3–5 times higher then that of morphine (ED50-3.39 mg/kg). At radioligand binding assay of 4c,e,f only compound 4f exhibited affinity for the μ-opioid receptors similar to that of Tramadol. The acute toxicity of the pyrrolopyridazinones 4, 5 were also studied and non toxic effect was observed at the 2000 mg/kg (5a 1420 mg/kg) i.p. dose level. On the basis of the available pharmacological data S-A relationship is discussed. The preferred conformational characteristic of 4, taken 4c as an example, was also described.

Chemical analysis of the secondary metabolite pattern of the aeolid nudibranch Phyllodesmium magnum collected from the South China sea resulted in the isolation of eight sesquiterpenes, exhibiting very different structural features, which included one asteriscane (1), two africanane (2, 3), one elemane (4), two selinane (5, 6), and two furano- (7,8) sesquiterpenes. Among them, compound 1, a new molecule, represents the fourth example of a rare asteriscane skeleton from a natural source, and the seven known sesquiterpenes (2-8) are new for P. magnum. The occurrence of the metabolites possessed by Phyllodesmium guamensis supports recent chemecological studies that it preys on the soft coral Sinularia sp., and uses these dietary chemicals as its defensive weapon. (C) 2011 Elsevier Ltd. All rights reserved.

Two bioactive natural 4-arylcoumarins, 5,7,4′-trimethoxy-4-phenylcoumarin ( 1a ), 5,7-dimethoxy-4-phenylcoumarin ( 1b ) and five closely related derivatives 1c – g were synthesized. In vitro evaluation with a catechol subunit for antioxidant and antimicrobial activity, these compounds using standard methods showed that compounds 1d , 1f displayed promise radical scavenging activity and 1f was found to be the most active one against Bacillus dysenteriae .

Despite of the extensive study for peptide synthesis, DCC-mediated esterification is left still unclear. Therefore, DCC- and DCC/HOBt-mediated reactions of 3-phenylpropionic acid (1) with benzyl alcohol were carried out under several mechanistic considerations. Further, in order to determine the reactivities of the so-called ‘active esters’ compounds changing the substituents bearing carbonyl and related derivatives group for the purpose of the development of new class of non-symmetry cross-linkers, we have studied the reaction of model compounds, N-(3-phenylpropionyloxy)benzotriazole (6), N-(3-phenylpropionyloxy)phthalimide (7), 3-phenylpropionyloxybenzothiazole (8), and N-(3-phenylpropionyl)benzotriazole (9) with various nucleophiles under similar conditions were carried out for the comparison. It was revealed to exhibit the order of 6>>8>9>7.

Chiral bicyclic diols based on bicyclo[2.2.2]octane and bicyclo[2.2.1]heptane have been synthesized and their catalytic capacity in the asymmetric diethylzinc addition to benzaldehyde compared with those described for previously synthesized 2,6-bicyclo[2.2.2]octane-diols (BODOLs). The influence of the number of coordinating sites and the distance between them were studied.

1,6-Anhydro-4-deoxy-4-diazo-2,3-O-isopropylidene-β- d -lyxo-hexopyranose (4) is a stable crystalline compound readily accessible by an improved synthetic procedure. It has been used as a model for evaluating the reactivity of the diazo group, when not stabilized by an adjacent carbonyl function, in a rigid chiral matrix. A range of carbene-type, electrophile-promoted, and 1,3-dipolar reactions were evaluated, leading to 4,4′-alkene dimers, 4-deoxy-3-enose and related derivatives, 4,4-dihalo compounds, 4-spirocyclopropane derivatives, 4-spiropyrazole structures, and by skeletal rearrangement, branched-chain anhydropentose structures having a bicyclo[2.2.2] skeleton.

The synthesis, in vitro evaluation, and structure-activity relationship studies of homoallylamines and related derivatives acting as antifungal agents are reported. Among them, compounds N-(4-bromophenyl)-N-(2-furylmethyl)amine and N-(4-chlorophenyl)-N-(2-furylmethyl)amine reported here exhibited remarkable antifungal activity against dermatophytes. Theoretical calculations allow us to determine the minimal structural requirements to produce the antifungal response and can provide a guide for the design of compounds with these properties.

Naturally occurring abietane quinones and hydroquinone, namely, 12-deoxyroyleanone (1a), cryptoquinone (4a), and 11,14-dihydroxyabieta-8,11,13-trien-7-one (5a), together with the epimers of tryptoquinones D (2) and F (3), were first synthesized from dehydroabietic acid (6).

Three new polyoxygenated briarane-type diterpenoids, briaexcavatolides X–Z ( 1-3 ), have been isolated from the gorgonian coral Briareum excavatum. The structures, including the relative configurations of briaranes 1-3 , were elucidated by spectroscopic methods, particularly in 1D and 2D NMR experiments. The configuration of briarane 1 was further supported by molecular mechanics calculations.

Amiloride and related derivatives, such as ethylisopropylamiloride (EIPA), are Na+/H+ exchange inhibitors that antagonize urokinase plasminogen activator (uPA) activity; however, their effect on the genesis of complex atherosclerotic lesions is unknown. Therefore, we sought to determine if (and how) EIPA reduces lesion formation in atherosclerosis-prone apoE-deficient (apoE−/−) mice. Eight-week-old male apoE−/− mice were fed an atherogenic diet with (n=10) or without (n=9) a continuous infusion of EIPA via a subcutaneous minipump (3 mg/kg/day) for 4 weeks. No significant differences were observed in the serum cholesterol levels, yet there was a 46% reduction in the en face aortic lesion size with EIPA treatment (control: 29.8±5.9% vs. EIPA: 16.1±4.8%; p

Flaxseed (Linum usitatissimum seed) is widely used in food and natural health products. In our search for osteoclast differentiation inhibitors, some cyclic peptides isolated from flaxseed, known as the cyclolinopeptides, were discovered to have osteoclast differentiation inhibition activity. The osteoclast differentiation inhibition activity of cyclolinopeptides A-I (1-9) and their related derivatives (10-14) are described herein. Cyclolinopeptides F, H and I (6, 8 and 9), in particular, showed potent osteoclast differentiation inhibition activity.

Efficient synthesis of (+)-2-aminobicyclo[3.1.0]hexane-2,6-dicarboxylic acid (LY354740: 1 ) and its structurally related analogs (−)- 2 and (−)- 3 has been accomplished starting with (1 S ,2 R )-1-amino-2-hydroxycyclopentane- or cyclohexanecarboxylic acid ( 4 or 17 ) via an intramolecular cyclopropanation of α-diazo acetamide.

The present paper describes studies on the synthesis of the antiepileptic drug phenytoin, and of structurally related derivatives. First, the influence of the solvent has been investigated in the microwave-assisted synthesis of the drug, resulting in a yield improvement and a cleaner reaction. Second; a two-step reaction is described to synthesize selectively and in high yields phenytoin. The first step consists in microwave activation of the reaction of benzil with thiourea, the second step includes the conversion of the resulting 2-thiohydantoin to phenytoin using hydrogen peroxide. Moreover, microwave activation is a very convenient method for the synthesis of 3-alkylated phenytoin derivatives, resulting in a much more selective method than the previously reported procedure using alkylating agents. (C) 2003 Elsevier Science Ltd. All rights reserved.

As observed by NMR, iodopyrroles 1a and 1b (ethyl and methyl 3,5-dimethyl-4-[(1′-iodo-2′,2′-dimethyl)propyl]pyrrole-2-carboxylate) and a variety of related derivatives with iodine replaced by methoxy 2 , thiomethyl 3 , acetic acid esters 4 , propionic acid ester 5 or malonic esters 6 exhibit restricted rotation about the C(4)C(1′) bond due to the bulky tert -butyl group and an ortho effect from the sterically crowded 3,5-dimethylpyrrole. Most of the compounds, which are members of the rare class of atropisomers due to restricted rotation about an sp 3 – sp 2 CC bond, undergo diastereomeric enrichment by preparative TLC and crystallization. From dynamic NMR studies of the enriched diastereomers one can determine kinetic and thermodynamic parameters associated with the atropisomerism, e.g., Δ G ‡ ∼24 kcal/mol for 1 and 5 (313 K), ∼22 kcal/mol for 3 (273 K), and ∼25 kcal/mol for 6 (313 K) in C 2 D 2 Cl 4 solvent.

Hydroboration of protected allylglycines with 9-BBN followed by Suzuki cross coupling of the resulting organoboranes proceeded smoothly giving a range of new bis-homophenylalanine and related derivatives in good yields (9 examples, 53–64%). One of the Suzuki coupling products has been elaborated to give the N-Cbz-protected natural product pyrimine. The hydroboration–Suzuki coupling of vinylglycine derivatives was also studied but was less efficient than with the allylglycine derivatives: the best results were obtained using disiamylborane·DMS as the hydroborating agent.

The complete spectroscopic data and other physical constants of two naturally occuring, diastereomeric, optically active γ-lactones derived from inexpensive 2-hydroxycitric acids, namely garcinia acid [(2S,3S)-tetrahydro-3-hydroxy-5-oxo-2,3-furandicarboxylic acid] and hibiscus acid [(2S,3R)-tetrahydro-3-hydroxy-5-oxo-2,3-furandicarboxylic acid] and related derivatives have been described for the first time.

The synthesis of two different sets of 3,3-disubstituted oxetane building blocks is described. These molecules can be usefully incorporated in more complex structures to modulate their metabolic and physicochemical properties. The synthetic pathways are general and could be exploited for the synthesis of many other related derivatives.

Flash vacuum pyrolysis (FVP) of 3-oxo-2-arylhydrazonopropanals at 500°C and 0.02 Torr yielded the corresponding derivatives of anilines, N -formylanilines, N -benzoylanilines and benzoylnitriles. Similar FVP of phenylhydrazonomalononitrile, phenylhydrazonoacetylacetone and phenylhydrazono ethyl cyanoacetate gave aniline in addition to N -cyanoaniline and 3,6-dicyano-1,4-diphenyl-1,2,4,5-tetrazine, acetanilide, N -methylacetanilide, pyruvonitrile and N -phenylurethane.

The review is focused on the (XPR 2 )(YPR′ 2 )NH acids (X, Y=O, S, Se; R, R′=alkyl, aryl, OR) and their main group metal derivatives. The methods of preparation, spectroscopic studies and molecular structures of known imidodiphosphorus acids and related derivatives as well as those of inorganic and organometallic main group metal complexes containing either protonated or deprotonated imidodiphosphorus ligand moieties are systematized and discussed.

In order to prepare new heterocyclic derivatives as building block for compounds with potential biological activities, we were led to study the O-methylation of 3-cyano-6-hydroxypyridine-2(1H)-ones such as 1. This enabled us to develop a new two steps method to prepare the corresponding 2,6-dimethoxy derivative 5 in 80 % yield. It consisted first in heating 1 in trimethylorthoformate, with or without an acidic catalyst, which gave a mixture of the two mono-methoxy isomers, then a classical methylation of the second hydroxy moiety led almost exclusively to 5. In this paper we present this “methylation” method and various unexpected results recorded when we attempted to extend it to related derivatives or to other heterocycle containing lactim-lactam functions. An intramolecular transetherification mechanism requiring the simultaneous transfer of a hydrogen and a methyl is suggested.

An efficient and novel process is described for the synthesis of nectrisine 5 and its related derivatives 6,7 as potent glucosidase inhibitors via the corresponding lactams starting from D-(−)-diethyl tartrate. Also the results of biological evaluation of the synthesized compounds are described.

A highly convergent approach has been developed for the construction of various nitrogen heterocycles using as the key step the intermolecular addition of an α-ketonyl radical onto a suitably protected allylic or homoallylic amine.

Two bioactive amino alcohols or related derivatives, 2-aminohexadecanol I and erythro-9-(2-hydroxy-3-nonyl)adenine hydrochloride (EHNA hydrochloride) IIa, have been synthesized from some enantiomerically pure 3-alkylglycerols. The required C-3 epimeric 3-alkylglycerols were, in turn, prepared by simple Grignard addition to cyclohexylideneglyceraldehyde 1 followed by column chromatography.

Structural characterization of [S(CH2CH2pzMe2)2]ZnCl2 by X-ray diffraction demonstrates that the potentially tridentate [NNS] donor ligand S(CH2CH2pzMe2)2 does not coordinate via sulfur, but only binds through the pyrazolyl groups. Furthermore, the ligand does not chelate, but preferentially bridges two zinc centers, thereby resulting in a polymeric, helical, structure. In contrast to the zinc system, the thioether functionality does bind to cadmium in related derivatives, [S(CH2CH2pzMe2)2]CdI2 and [S(CH2CH2pzMe2)2]Cd(NO3)2.

Decomposing a tertiary diazo derivative in the presence of a dithionodisulfide gives the corresponding tertiary thionosulfide (xanthate, dithiocarbamate, or dithioester) in good yield.

Heating carboxylic acids with O-benzyl-S-propargyl xanthate in refluxing toluene gives the corresponding benzyl esters in high yield; other acidic substances such as tetrazoles and pyridinols are benzylated selectively under the same conditions.

γ-hydroxyalkenylstannanes, readily available from α,β-unsaturated esters, α,β-unsaturated aldehydes and tri(n-butyl)stannyllithium, react with boron trifluoride etherate to produce vinyl cyclopropane carboxylic esters. An original highly convergent synthesis of chrysanthemic acid is reported.

N-Alkylated derivatives of pipecolic acid are shown to undergo highly stereoselective oxidation to give stable tertiary amine N-oxides. The ester derivatives show a high degree of stability compared to their proline analogues.

Methyl 3-methyljasmonate was synthesised from methyl jasmonate via methyl 3,7-dehydrojasmonate. Molecular modelling predicted an increase in the proportion of cis -orientated side-chains for equilibrated 3-methyl-substituted jasmonate. The synthetic 3-methyljasmonate was shown by gc-ms analysis to equilibrate to a 2:1 ratio of isomers, which appeared from the NMR spectra to comprise mainly the cis -isomer. Surprisingly, both 3,7-dehydro- and 3-methyl-derivatives were inactive in four well established jasmonate bioassays. Methyl-2-methyljasmonate was synthesised and also found to be inactive. Methyl 4,5-dehydrojasmonate was prepared, via the 5-diazo derivative. Both of these compounds have low activity. Our results are discussed with reference to previous knowledge of jasmonate structure-activity relationships and indicate that there are stringent steric demands in jasmonate-receptor interactions.

Conformational and electronic studies of 3-tigloyl-azadiractol and other azadirachtin derivatives were carried out using molecular mechanics and AM1 calculations. A comparative analysis of the conformational characteristics of 3-tigloyl-azadirachtol, azadirachtin and its structurally related derivatives was also performed. Our results indicate that the lack of antifeedant activity of 7-ketoazadirachtin and other inactive compounds can be explained on the basis of their different conformational behaviour. The conformationally restricted azadirachtin analogues provide us with crucial information about the optimal conformational requirement necessary to stimulate an antifeedant response.

Hapalosin possessing a multidrug resistance reversing activity, has been synthesized from the corresponding hydroxy acids and γ-amino acids. The stereochemistry of the natural product and related derivatives is discussed.