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Radicinin is a phytotoxic dihydropyranopyran-4,5-dione isolated from the culture filtrates of Cochliobolus australiensis, a phytopathogenic fungus of the invasive weed buffelgrass (Cenchrus ciliaris). Radicinin proved to have interesting potential as a natural herbicide. Being interested in elucidating the mechanism of action and considering radicinin is produced in small quantities by C. australiensis, we opted to use (±)-3-deoxyradicinin, a synthetic analogue of radicinin that is available in larger quantities and shows radicinin-like phytotoxic activities. To obtain information about subcellular targets and mechanism(s) of action of the toxin, the study was carried out by using tomato (Solanumlycopersicum L.), which, apart from its economic relevance, has become a model plant species for physiological and molecular studies. Results of biochemical assays showed that (±)-3-deoxyradicinin administration to leaves induced chlorosis, ion leakage, hydrogen peroxide production, and membrane lipid peroxidation. Remarkably, the compound determined the uncontrolled opening of stomata, which, in turn, resulted in plant wilting. Confocal microscopy analysis of protoplasts treated with (±)-3-deoxyradicinin ascertained that the toxin targeted chloroplasts, eliciting an overproduction of reactive singlet oxygen species. This oxidative stress status was related by qRT-PCR experiments to the activation of transcription of genes of a chloroplast-specific pathway of programmed cell death.

Radicinin is a phytotoxic dihydropyranopyran-4,5-dione isolated from the culture filtrates of Cochliobolus australiensis, a phytopathogenic fungus of the invasive weed buffelgrass (Cenchrus ciliaris). Radicinin proved to have interesting potential as a natural herbicide. Being interested in elucidating the mechanism of action and considering radicinin is produced in small quantities by C. australiensis, we opted to use (±)-3-deoxyradicinin, a synthetic analogue of radicinin that is available in larger quantities and shows radicinin-like phytotoxic activities. To obtain information about subcellular targets and mechanism(s) of action of the toxin, the study was carried out by using tomato (Solanum lycopersicum L.), which, apart from its economic relevance, has become a model plant species for physiological and molecular studies. Results of biochemical assays showed that (±)-3-deoxyradicinin administration to leaves induced chlorosis, ion leakage, hydrogen peroxide production, and membrane lipid peroxidation. Remarkably, the compound determined the uncontrolled opening of stomata, which, in turn, resulted in plant wilting. Confocal microscopy analysis of protoplasts treated with (±)-3-deoxyradicinin ascertained that the toxin targeted chloroplasts, eliciting an overproduction of reactive singlet oxygen species. This oxidative stress status was related by qRT-PCR experiments to the activation of transcription of genes of a chloroplast-specific pathway of programmed cell death.

The stereoselective transformation of chiral UV-transparent amines and alcohols to phthalimides has proved to be a simple and efficient method to enhance the chiroptical response of these substrates allowing their reliable absolute configuration determination by computational analysis of ECD spectra. Such a transformation also leads to a significant reduction in the molecular conformational flexibility thus simplifying the conformational analysis required by the computational treatment. The method described herein thus allows the absolute configuration assignment to these challenging substrates to be much easier and reliable.

The inter-molecular carbolithiation of unfunctionalized and functionalized alkenes, followed by electrophile trapping, provides a versatile and useful tool for the construction of complex molecular systems, allowing the simultaneous creation of up to two novel carbon–carbon or carbon–heteroatom bonds. In this review a full overview on inter-molecular carbolithiation processes is reported, with a main focus on the chemo-, regio- and stereo-control of the reaction and on the strategies for asymmetric processes.

The absolute configuration of chiral 2-aryl and 2-aryloxy propionic acids, which are among the most common chiral environmental pollutants, has been readily and reliably established by either electronic circular dichroism spectroscopy or optical rotation measurements employing suitably designed 4,4′-disubstituted biphenyl probes. In fact, the 4,4′-biphenyl substitution gives rise to a red shift of the diagnostic electronic circular dichroism signal of the biphenyl A band employed for the configuration assignment, removing its overlap with other interfering dichroic bands and allowing its clear sign identification. The largest A band red shift, and thus the most reliable results, are obtained by employing as a probe the 4,4′-dinitro substituted biphenylazepine 3c. The method was applied to the absolute configuration assignment of 2-arylpropionic acids ibuprofen (1a), naproxen (1b), ketoprofen (1c) and flurbiprofen (1d), as well as to the 2-aryloxypropionic acids 2-phenoxypropionic acid (2a) and 2-naphthoxypropionic acid (2b). This approach, allowing us to reveal the sample’s absolute configuration by simple optical rotation measurements, is potentially applicable to online analyses of both the enantiomeric composition and absolute configuration of these chiral pollutants.

The application of flexible biphenyls as chiroptical probes for the absolute configuration assignment to chiral natural products is described. The method is straightforward and reliable and can be applied to conformationally mobile and ECD silent compounds, not treatable by computational analysis of chiroptical data. By this approach, the (6′R) absolute configuration of the phytotoxin colletochlorin A (1) was confirmed, while the absolute configuration of the phytotoxin agropyrenol (2), previously assigned by the NMR Mosher method, was revised and assigned as (3′S,4′S). Moreover, with the biphenyl method the configurational assignment can be obtained simply by the sign of a diagnostic Cotton effect at 250 nm in the ECD spectrum, thus allowing application without the need of advanced knowledge of chiroptical spectroscopy and computational protocols.

Jonquailine, a new alkaloid recently isolated from Narcissus jonquilla quail, an Amaryllidaceae species cultivated for its flowers fragrance in Europe and USA, shows very significant anti-proliferative activity against several , malignant cancer cell types. Although it was reported that this activity is related to the functionalities and to its stereochemistry at C-8 of B ring, the absolute configuration at this stereocenter was not known. Density functional theory (DFT) calculations of chiroptical properties, namely electronic circular dichroism (ECD), vibrational circular dichroism (VCD), and optical rotatory dispersion (ORD) are employed here to complete assignment of absolute configuration of jonquailine, and then, by extension, to its analogues pretazettine and 8-Omethylpretazettine. While ECD is not discriminating and ORD is of limited use, VCD reveals decisive in the task of absolute configuration assignment.

The first asymmetric total synthesis of both enantiomers of the natural products colletorin A and colletochlorin A is presented. The proposed methodology is based on the coupling reaction between highly substituted aromatic Gilman cuprates and optically active allyl bromides, in turn obtained by Sharpless asymmetric dihydroxylation. The latter ensured a high degree of regio- and stereocontrol in the enantioselective step of the synthesis. The same synthetic strategy has been also applied for the preparation of differently halogenated synthetic analogues of colletochlorin A in high enantiomeric purity. The enantioselective synthesis of colletorin A and colletochlorin A allows to reliably assign their absolute configuration. Preliminary assessment of their herbicidal and insecticidal properties evidence the possibility to modulate the bioactivity of these compounds, highlighting its dependence on both the absolute stereochemistry and the halogen nature.

Green Chemistry, Circular Economy and Sustainability are issues at the center of the modern scientific debate and three major trends in the global market. These three subjects are interconnected and interdependent and represent an affordable set of principles bringing innovations in the management of complex processes connected with anthropic use of resources.

The fungal pathogen Pyricularia grisea has been studied to evaluate its production of phytotoxins for the biocontrol of the buffelgrass (Cenchrus ciliaris L.) weed. A first investigation allowed to isolate several new and known phytotoxic metabolites. However, the further investigation on the organic extract obtained from the fungus liquid culture showed the presence of other metabolites possibly contributing to its phytotoxicity. Thus, four known metabolites were isolated and identified by spectroscopic (nuclear magnetic resonance [NMR] and high-resolution electrospray ionization mass spectrometry [HRESIMS]) methods as dihydropyriculol (1), epi-dihydropyriculol (2), 3-methoxy-6,8-dihydroxy-3-methyl-3,4-dihydroisocoumarin (3), and (R)-mevalonolactone (4). The absolute configuration of 1-3 was determined for the first time by a computational analysis of their electronic circular dichroism (ECD) spectra. When the isolated compounds were bioassayed at a concentration of 5 × 10-3 M in a buffelgrass coleoptile and radicle elongation test no toxicity was detected. On the contrary, compounds 1 and 3 showed a significant stimulating effect of radical elongation. Furthermore, the difference in growth stimulation between 1 and its epimer 2 highlights the tight relationship between absolute configuration and biological activity of these fungal metabolites.

A novel synthetic strategy for obtainment of (&plusmn, )-3-deoxyradicinin (2) is reported. This synthetic methodology is more efficient than those previously reported in the literature and also shows higher versatility towards the introduction of different side-chains at both C-7 and C-2. The obtained compound (&plusmn, )-2 shows phytotoxicity against the grass-weed buffelgrass comparable to that of the natural phytotoxin radicinin (1). Therefore, (&plusmn, )-2 can constitute a more practical synthetic alternative to 1 as bioherbicide for buffelgrass control.

A non-empirical approach for the assignment of the absolute configuration of chiral 2-alkyl-substituted carboxylic acids and primary amines by [α]D measurements has been developed. The method requires the conversion of the chiral acids or amines into the corresponding 4,4'-disubstituted biphenylamides or biphenylazepines, respectively. In these derivatives a central-to-axial chirality transfer induces a preferred torsion in the biphenyl moiety revealed by the sign of the biphenyl A band in the ECD spectrum. By 4,4'-substitution on the biphenyl moiety a redshift of the A band is obtained, leading to an increase of its relative contribution to optical rotation. This allows to reliably establish a direct correlation between the [α]D sign, the biphenyl twist and, then, the substrate absolute configuration. This approach thus constitutes a really practical and reliable method to assign the absolute configuration of chiral carboxylic acids and primary amines by simple and straightforward [α]D measurement, readily obtainable by a routine instrumentation like the polarimeter.

Flexible biphenyls have been applied as efficient and practical chiroptical probes for absolute configuration assignment to chiral primary amines. The mechanism of the central-to-axial chirality transfer from the amine moiety to the conformationally flexible biphenyl system has been determined by NMR and computational studies. This allowed proposing a general non-empirical rule in order to establish, simply by looking at the sign of the 250 nm A band in the ECD spectrum of the biphenyl derivative, the torsion of the biphenyl and thus the absolute configuration of the amine. The method proved to be very reliable and sensitive, allowing treatment of samples on the μmol scale and permitting the simultaneous determination of the amine sample's absolute configuration and enantiopurity.

The preparation of new chiral amino alcohols that possess a flexible biphenylazepine moiety and can work as tropos catalysts, is presented. In these compounds, the sign of the induced axial chirality depends on the nature of stereogenic centers near the flexible fragment and can determine the stereochemical outcome in asymmetric reactions mediated by them. The efficiency of these new ligands has been explored in the asymmetric addition of arylzinc species prepared in situ to aromatic aldehydes. Among them, amino alcohol (1R,2S)-4 gave the best results and afforded optically active diarymethanols, which are precursors of well-known chiral drugs, in high yields and with enantioselectivity up to 96 %.

Three forms of chiroptical spectroscopies, electronic circular dichroism (ECD), vibrational circular dichroism (VCD), and optical rotatory dispersion (ORD) have been employed to study the configuration and conformational properties of the three molecules: (S)-3-phenylcyclopentanone, (S)-3-phenylcyclohexanone, and (S)-3-phenylcycloheptanone (including (S)-3-phenylcyclopentanone-2,2,5,5-d4 and (S)-3-phenylcyclohexanone-2,2,6,6-d4). ECD and VCD spectra in the mid-IR for the three molecular systems are marginally dependent on fine conformational details, as interpreted in terms of standard DFT computational methods, with common spectroscopic features to the three systems clearly identified. Accounting for vibronic coupling mechanisms reproduces the structuring of ECD n→π∗ band. The ORD curves are quite similar for the three types of molecules, but their interpretation highlights a crucial role played by conformations of the cycloalkanone ring in the case of (S)-3-phenylcycloheptanone. The same conclusions are reached by considering the VCD spectra in the CH-stretching region.

Background: Quantum mechanical simulations of chiroptical properties, such as electronic circular dichroism (ECD), optical rotation (OR), and vibrational circular dichroism (VCD), have rapidly become very popular to assign the absolute configuration of novel natural products. Objective: We review the application of the ECD/OR/VCD computational methodology to chiral metabolites of fungal origin. First, we summarize the fundamentals of the three spectroscopies; then, we focus on the specific experimental and computational issues allied to the application of their calculations. Methods: We surveyed the entire literature describing the use of ECD/OR/VCD computations for fungal metabolites, and catalogued all papers according to the method employed and to the structural family of compounds. Then, we chose several examples to illustrate the use of the techniques and highlight the practical application of the computational approach. Results: Our literature survey demonstrates that the simulation of ECD/OR/VCD spectra is nowadays widespread and accessible also to non-experts, although a good computational practice is necessary to avoid wrong assignments. ECD is still the most common technique used in the context of fungal metabolites. OR and VCD may be profitably employed when the compound of interest lacks chromophoric groups. Our examples illustrate that the combination of two or more chiroptical methods is strongly advisable in some cases, especially in the presence of high conformational flexibility, where a single technique does not lead to a safe conclusion. Conclusion: The ECD/OR/VCD computational approach is a reliable and versatile method to assign the absolute configuration of fungal metabolites and related natural products.

A versatile and straightforward approach to optically active cis -4,5-disubstituted γ- and δ-lactones by catalytic enantioselective addition of dialkyzincs to cinnamic aldehydes and RCM ring closure has been reported. The synthetic importance of the enantioselective dialkylzinc alkylation of aldehydes has been thus widened. Such an approach has then been employed for the enantioselective synthesis of naturally occurring γ-lactone flavors like ( S )-5-ethyl-butanolide ( 6a ) and (4 S ,5 S )- cis -whisky lactone ( 6b ) and extended to the preparation of δ-lactones like (5 S ,6 S )-5-methyl-6-ethylpentanolide ( 9a ), precursor of the pheromone serricornin.

Herein we report the asymmetric addition of phenylboronic acid to different cycloalkenones, mediated by a Rh(I) complex with the tropos phosphoramidite ( S )- L 1 or the nontropos phosphoramidite ( S )- L 2 ligand. Different values of enantiomeric purity of the 3-phenylcycloalkanone products have been obtained, mainly depending on the ring size of the substrates, with ( S )- L 1 affording higher ee values than ( S )- L 2 . These results could be explained by reasoning that for the tropos phosphoramidite, a ‘chiral pocket’ is formed when the ligand links to the metal atom. By fitting in this pocket, the substrate can stereoselectively coordinate to the Rh(I) atom, undergoing attack of the phenyl ring from the phenylboronic acid to a preferred enantioface. This causes the high (up to 96%) values of enantioselectivity observed with some of the substrates. A ‘chiral pocket’ cannot be formed with the nontropos ligand ( S )- L 2 and, as a consequence, the stereoselectivity is greatly reduced.

A new simple route to (+)-cis-2-methyl-4-propyl-1,3-oxathiane, the main component responsible of the passion fruit aroma is shown. Such a procedure consists in the sequence of the asymmetric conjugated addition of a thiol to trans-2-hexenal/cleavage of sulfide moiety, which allows to prepare, in only two steps, its immediate precursor, (R)-3-mercaptohexan-1-ol. Various procedures have been investigated for both the steps, using benzyl and tert-butyl mercaptan as thiols. The best results have been achieved in the addition of benzyl thiol to trans-2-hexenal mediated by a proline-derived organocatalyst, followed by debenzylation with sodium naphthalenide, affording (R)-3-mercaptohexan-1-ol with 84% e.e. and a yield much higher (32%) than that previously reported (8.5%). Chirality, 2009. © 2008 Wiley-Liss, Inc.

By reacting flexible and optically transparent in UV-vis molecules such as 1,2-, syn- and anti-1,3-diols, 1,3-sulfanylalcohols of known absolute configuration (AC) with fluorenone dimethyl acetal, the corresponding ketals are obtained. They are conformationally well-defined (only one conformer in most cases) compounds exhibiting medium-high optical rotation (OR) values, which are independent of the solvent, and electronic circular dichroism (ECD) spectra, which show several (up to five) Cotton effects in the 350-200 nm range due to valence shell pi--pi* transitions. These features allow simulation of the chiroptical properties of these compounds at the TDDFT/B3LYP/6-31G* level of theory to obtain, using the known ACs of these compounds, a satisfactory reproduction of the OR values (sign and order of magnitude; quantitatively, the predicted values are twice the experimental ones), and a more than satisfactory reproduction of the ECD spectra (sign, intensity, and position of the lowest-energy four Cotton effects) for all the compounds studied. Therefore, this approach can be used to assign the AC of such flexible molecules, in particular, syn-1,3-diols, which are important substrates in organic synthesis and for which nonempirical methods of AC assignment have not been devised so far. Furthermore, since the fluorene chromophore leads to the presence of several Cotton effects from, say, 350 to 200 nm, their correct simulation of sign, intensity, and position is a guarantee of the correct assignment of AC: in this way, ECD spectroscopy gains the same advantages of VCD spectroscopy, that is, the need of reproducing many ECD bands and then a solid guarantee of a correct AC assignment.

The effects of the substitution on the aryl moiety on the asymmetric oxidation of sulfides mediated by Ti-complexes of chiral 1,2-diarylethane-1,2-diols were investigated. The substitution of the aryl ring of the diol with both EWG and EDG substituents generally decreased the enantioselectivity with respect to the use of unsubstituted 1,2-diphenylethane-1,2-diol (1a). Only in the presence of 1,2-di(4-t-butyl)phenyl-1,2-diol (1g) were higher ee's obtained with aryl methyl and aryl benzyl sulfides affording ee's up to 90 and 99%, respectively. Lower ee's were achieved with larger naphthyl and aryl alkyl sulfides. Contrary to the other Ti-alcoholates used in the oxidation of sulfides, the Ti-complex of diol 1g was soluble in hexane, allowing us to perform the process with high enantioselectivity in this solvent, with great environmental advantages over the commonly used chlorinated solvents. Chirality, 2008. © 2008 Wiley-Liss, Inc.

The preparation of new chiral amino alcohols that possess a flexible biphenylazepine moiety and can work as tropos catalysts, is presented. In these compounds, the sign of the induced axial chirality depends on the nature of stereogenic centers near the flexible fragment and can determine the stereochemical outcome in asymmetric reactions mediated by them. The efficiency of these new ligands has been explored in the asymmetric addition of arylzinc species prepared in situ to aromatic aldehydes. Among them, amino alcohol (1R,2S)-4 gave the best results and afforded optically active diarymethanols, which are precursors of well-known chiral drugs, in high yields and with enantioselectivity up to 96 %.

We show herein an alternative catalytic, highly enantioselective approach to ( R )-12-methyltridecanolide and ( S )-muscolide, that is, chiral macrocyclic lactones which are good musk odorants. In fact, they can be efficiently prepared by a sequence of reactions consisting of a catalytic asymmetric conjugated addition of dimethylzinc to suitable α,β-unsaturated enones followed by a Baeyer–Villiger oxidation. Interestingly, high enantiomeric excesses (up to 92%) are obtained in the asymmetric conjugate addition by means of the ‘tropos’ phosphoramidite L1 .

The stereoselective synthesis of the fragrance trans-magnolione (1) through conjugate Michael addition of alkyl acetoacetates to 2-pentyl-2-cyclopentenone (2) under solid/liquid phase transfer catalysis (PTC) is reported. Under optimized conditions, the 1,4-addition of tert-butyl acetoacetate to enone 2 catalyzed by N-9-anthracenylmethylquininium chloride (4) affords, after hydrolysis and decarboxylation, trans-(2S,3S)-1 with 85/15 d.r. and 74% ee. The use of the pseudo-enantiomeric catalyst N-9-anthracenymethylquinidinium chloride (5) allows obtaining the enantiomer trans-(2R,3R)-1 with comparable enantio- and diastereoselectivity. To cite this article: S. Superchi et al., C. R. Chimie 8 (2005).

The preparation of a new phosphoramidite starting from ( R )-BINOL and a biphenylamine is presented. In such a compound the chirality is due only to atropisomerism and this molecule possesses a flexible biphenylamine residue. Therefore it can work as a tropos catalyst. The catalytic efficiency of this new phosphoramidite has been tested in some asymmetric conjugate additions of dialkylzinc reagents to α,β-enones and compared with that of an analogous already known non-tropos ligand. Interestingly, while comparable results were obtained in the addition of ZnEt 2 to chalcone and cyclohexenone, in the case of the addition of ZnMe 2 to ( E )-cyclopentadec-2-en-1-one, the new ligand provides (−)-muscone, a valuable ingredient of the perfume industry, in 84% ee, while the non-tropos ligand gives a much lower (57%) ee value.

Four phosphites, obtained by linking enantiomerically pure binaphthylchlorophosphite to the two different hydroxy substituted positions of deoxycholic acid, were used as chiral ligands in the enantioselective copper catalysed 1,4-addition of diethylzinc to 2-cyclohexenone and dimethylzinc to 2-cyclopentadecenone. Various reaction parameters were changed in order to select the experimental conditions that would maximise yield and ee. The four ligands were screened for activity and enantioselectivity under the optimised reaction conditions for comparative purposes, in order to establish the influence of the absolute configuration of the binaphthyl moiety as well as the position on the cholestanic backbone of the phosphite moiety. The ligand possessing a ( R )-binaphthylphosphite moiety at position 12 of the cholestanic backbone proved to be the most enantioselective affording (−)-( R )-muscone in 63% ee.

Both enantiomers of the trans stereoisomer of magnolione 4 have been prepared by asymmetric Michael addition of ethyl acetoacetate to 2-pentylcyclopentenone, followed by hydrolysis/decarboxylation. The Michael reaction occurs under solid/liquid phase transfer catalysis in the presence of N -methylanthracenylquininium (or quinidinium) chloride. Enantiomeric excesses up to 76% are obtained. The trans structure of the compounds has been fully established by a careful NMR analysis, while the absolute configuration has been assigned as (2 S ,3 S ) for (+)- 4 by the analysis of the CD spectrum.

New diastereoisomeric phosphites based on either (R)- or (S)-2,2′-dihydroxy-1,1′-binaphthyl (BINOL) and having the chiral alcoholic moiety derived from the monobenzyl ether of (R,R)-1,2-diphenylethane-1,2-diol have been prepared and used as chiral ligands in the enantioselective copper-catalyzed 1,4-addition of diethylzinc to chalcone and 2-cyclohexen-1-one (enantiomeric excesses up to 48%). With the (aR,R,R) ligand dimethylzinc adds enantioselectively to (E)-cyclopentadecen-2-en-1-one to give (R)-(−)-muscone (68% yield, 78% ee). This provides an efficient access to a valuable ingredient of the perfume industry. However, with the (aS,R,R) ligand, (S)-(+)-muscone is obtained with longer reaction times (37% yield and 10% ee) with a very high double diastereoselection effect being observed.

We report the conformational analysis of three chiral cyclic sulfoxides, 1-thiochroman-4-one S-oxide (1), 1-thiaindan S-oxide (2), and 1-thiochroman S-oxide (3). Vibrational unpolarized absorption (IR) and vibrational circular dichroism (VCD) spectroscopies are employed, in combination with ab initio density functional theory (DFT). DFT calculations predict two, two, and three conformations with energies spanning

By rational design, novel atropisomeric 1,1-binaphthylazepine-based 1,2-amino alcohols 1f and 1g have been prepared in enantiopure form and tested as catalytic precursors in the enantioselective addition of diethylzinc to aromatic aldehydes: the corresponding ( S )-1-arylpropanols have been obtained in quantitative yields and e.e.s up to 95%. A rationale explaining the stereochemical outcome of the reaction, as well as the influence of structural features of the ligands on the enantioselectivity of the addition, is also provided.

The monobenzylethers of ( R , R )-1,2-diphenylethane-1,2-diol have been used as chiral auxiliaries in the stereoselective reduction of the corresponding phenylglyoxylates. The diastereoselectivity of the reduction with either l -selectride or DIBAL was found to be strictly dependent on the nature of the substitution on the aromatic ring of the auxiliary and a maximum d.r. of 87:13 was obtained with the p -CF 3 substituted derivative. This investigation also shows that with open chain chiral auxiliaries diastereoselectivities of preparative interest can be achieved, suggesting that such auxiliaries can constitute a promising alternative to the commonest cyclohexyl-based ones.

We have determined the absolute configuration of the chiral sulfoxide 1-thiochroman S-oxide 1 using vibrational circular dichroism (VCD) spectroscopy. The VCD spectrum of a CCl4 solution of 1 was analyzed using density functional theory (DFT), which predicts three stable conformations of 1, separated by

The reliable determination of the absolute configuration of (+)- endo-2- norborneol 1 , chosen as a representative case of simple aliphatic UV–vis transparent alcohols, was obtained by transforming this compound in its 1-naphthyl-diphenylmethyl ether 5 whose ECD spectrum displays several, low-lying, intense Cotton effects, which can be satisfactorily simulated in position, sign, and intensity by TDDFT/B3LYP/6-31G ∗ calculations. This result represents a possible, general, new approach to the absolute configuration of aliphatic alcohols.

o-Aminothioaldehydes derived from benzo[ b ]furan, benzo[ b ]thiophene, indole and furan rings smoothly react with mono- and disubstituted electron deficient alkynes to give b -fused dihydropyridines which can be converted to corresponding pyridines upon heating under vacuum.

The reaction of hexamethyldisilathiane (HMDST) with different carbonyl compounds affords, under the catalysis of CoCl2.6H2O or CF3SO3SiMe3 a general access to several thioaldehydes and thioketones including acetylenic derivatives and thioformylsilanes. The use of CF3SO3SiMe3 allows a stereopredetermined entry to both the endo or the exo isomers when cyclohexadiene is used as the trapping agent. Furthermore, when using aromatic and heteroaromatic o-azidoaldehydes, the reactional behavior of HMDST may well be finely tuned to drive the reaction toward the synthesis of o-azidothioaldehydes, fused isothiazole ring systems, aromatic and heteroaromatic o-aminoaldehydes and o-amino thioaldehydes. Finally, taking advantage of the high reactivity of the C-Si bond under fluoride ion catalysis, a selective regiospecific thiophilic functionalization of thioketones, dithioesters, trithiocarbonates and their sulfines by different organosilanes can be obtained.

This paper describes the enantioselective synthesis of analogues of sapinofuranones A and B, namely 5-substitutes dihydro- and 5 H-furan-ones, and their in vitro growth inhibitory activity against six cancer cell lines in comparison with fungal furanones such as diplofuranone A, diplobifuranylones A and B, as well as ( S,S)-enantiomer of sapinofuranone B. The compounds under study displayed weak if any in vitro growth inhibitory activity against the analysed cancer cell lines. However, it seems that among dihydro- and 5 H-furan-ones bearing a 1-hydroxypentyl side chain, the stereochemistry of the furanone ring and that of hydroxylated methine could modify the in vitro growth activity of these compounds. The natural furanones that showed a different unsaturated chain at C-4 or rearranged into a dihydrofuran ring appeared to be inactive in terms of growth inhibitory activity, e.g. displaying growth inhibitory concentration at 50% (GI50) > 100 μM in all six cancer cell lines analysed.