Dipartimento di Scienze Chimiche e Farmaceutiche

(R)-(+) and (S)-(À)-1-phenylethylamine have been shown to promote highly diastereoselective and complementary enantioselective formal [3 + 2]carbocyclization reactions between 2, 3-butanedione and conjugated nitroalkenes with formation of enantiomerically rich 2-hydroxy-3nitrocyclopentanone derivatives. The reactions were carried out both in solvent and under solventfree conditions. The absolute configurations of the products were assigned by X-ray and circular dichroism spectra analyses. Chirality 00:000-000, 2012.

The behaviour under electron impact of six 1,l-bis(benzenesulphony1)cycloalkanes and of l-phenyl-l-(benzensesulphonyl)cyclopropane has been studied in detail with the aid of exact mass measurements, linked scans for metastable ion analysis, collisional spectroscopy and kinetic energy release measurements. The molecular ions of these compounds undergo a sulphon-ulphinate rearrangement with alkyl group migration on oxygen, in analogy with what is found for simple monosulphones and, in general, their fragmentation resembles that of monosulphonyl compounds. Loss of SO2 from the molecular ion is observed for all substrates, but only in the case of 1,l-bis(benzenesulphony1)cyclopropane is this followed by loss of the second SO, unit; the first loss of SO, is probably accompanied by rearrangement since the fragmentation pattern of [M-SO,]" ions from this compound is different than that of the isobaric molecular ions of 1-phenyl-l-(benzenesdphonyl)cyclopropane.

Acetic acid bacteria (five strains of Acetobacter and five strains of Gluconobacter) were used for the biotransformation of different primary alcohols (2-chloropropanol and 2-phenylpropanol) and diols (1,3-butandiol, 1,4-nonandiol and 2,3-butandiol). Most of the tested strains efficiently oxidized the substrates. 2-Chloropropanol and 1,3-butandiol were oxidized with good rates and low enantioselectivity (enantiomeric excess = 18-46% of the S-acid), while microbial oxidation of 2-phenylpropanol furnished (S)-2-phenyl-1-propionic acid with enantiomeric excess (e.e.) >90% with 10 strains. The dehydrogenation of 2,3-butandiol was strongly dependent on the stereochemistry of the substrate; the meso form gave S-acetoin with all the tested strains, the only exception being a Gluconobacter strain. The formation of diacetyl was observed only by using R,R-2,3-butandiol with Acetobacter strains. Oxidation of 1,4-nonandiol gave ␥-nonanoic lactone in one step, although with moderate enantioselectivity.

A series of yeasts were used in the bioreductions of aliphatic and aromatic gand d-ketoacids and esters to investigate the preparation of enantiomerically pure gand d-lactones through the intermediacy of their corresponding gand d-hydroxyacids and esters. Bioreduction of ethyl 4-oxononanoate 2a with Pichia etchellsii afforded the g-nonanolide (+)-5a with 99% e.e., while Pichia minuta proved to be the best choice for the bioreduction of ethyl 2-oxocyclohexylacetate 2e, which afforded cis-(−)-5e and trans-(−)-5e with 98 and 99% e.e., respectively. Reduction of 3-(2-oxocyclohexyl)propionic acid 3e with Pichia glucozyma gave predominantly the corresponding d-lactone trans-(−)-6e with 94% e.e., whose absolute configuration was determined by means of CD spectroscopy.

Baker's yeast reduction of 3-(2-nitroethyl)-tetrahydro-4H-pyran-4-one 10 and 3-(2-nitroethyl)-tetrahydro-4H-thiopyran-4-one 11 gave the corresponding optically active cis alcohols with good diastereo-and enantioselectivity. The unreacted optically active ketones were also isolated. (~) 1997 Elsevier Science Ltd

Enantiomerically pure condensed δ-lactones have been prepared from the corresponding δ-ketoesters by the use of Saccharomyces cerevisiae. The reactions were not only highly enantioselective but also highly diastereoselective, provided the baker's yeast was preincubated at 50°C for 30 min. Interestingly, and contrary to what is usually found, the use of nutrients inhibited the bioreductions. The relative configurational assignments have been made by means of NMR, while the absolute configurations and conformations of the lactone rings were attributed by means of CD studies.

The formation of enantiopure d-lactones condensed with alicyclic rings has been achieved either by reduction with baker's yeast of the corresponding d-keto esters and d-keto acids or by enzymic resolution of the former compounds. The absolute con®gurations of the lactones were determined by means of CD spectroscopy, using the correlation method.

Paraconic acid 4, (S)-())-terebic acid 6 and their corresponding methyl and ethyl esters having eeÕs ranging from 60% to 92% were obtained by enzymatic resolution of their racemates. The enzymatic resolution of racemic ethyl c-methylparaconates 14a and 14b allowed the isolation of the unreacted ester (2R,3R)-(+)-14a and that of the lactonic acid (2S,3R)-())-5b with 80% and 93% ee, respectively, the former by the use of Horse liver acetone powder (HLAP), the latter using a-chymotrypsin (a-CT). The enantiomeric ethyl (2S,3S)-())-14a and (2S,3R)-())-14b, both with >99% ee, were obtained by bakerÕs yeast reduction of diethyl acetylsuccinate.

Enantiopure (99% ee) cis-and trans-c-benzylparaconic acids and their ethyl esters were synthesized by a procedure involving kinetic enzymatic resolution of the corresponding lactonic esters with a-chymotrypsin (a-CT) with acetone added as a cosolvent. Their absolute configurations were determined by 1 H NMR analysis of their 1-(9-anthryl)-2,2,2-trifluoroethyl esters.

The natural fragrances (+)-trans whisky lactone 2 and (+)-trans cognac lactone 4, together with a minor amount of their (À)cis stereoisomers, were prepared in 50% and 42% overall yield, respectively, starting from racemic 1-hepten-3-ol (±)-5 and 1-octen-3-ol (±)-6. The procedure involved first the enantioconvergent, lipase mediated transformation of the secondary allylic alcohols derived dichloroacetates (±)-7 and (±)-8 into the corresponding homochiral (+)-7 and (+)-8, combined with their cyclization under a transition metal catalyzed atom transfer process.

Application of 1,3-Azomethine Ylides Derived from α-Dicarbonyl Compounds and L-Proline to the Synthesis of Pyrrolizidines.-The one-pot three-component reaction between diacetyl compounds (I), β-nitrostyrene (II), and L-proline (III) in isopropanol at room temperature affords the regioisomeric cycloadducts (IV) and (V). In contrast, the cycloadduct (XI) is formed from cyclohexanedione (X) only when the reaction is performed in refluxing isopropanol. At room temperature incorporation of the amine component into the products fails and bicyclooctanones (XII) and (XIII) are the result of a tandem Michael-Henry reaction. In this case L-proline acts as a catalyst, although with modest enantioselectivity. In order to determine the mechanism of formation of the pyrrolizidines, a reaction is performed between butanedione (Ia), (II), and hydroxyproline (VI), thus taking advantage of the presence of a stereocenter of known configuration.

Botryodiplodin and (±)-epi-botryodiplodin acetates were prepared in good yields following a practical four step route. The method, for the construction of the strategic tetrahydrofuran ring, hinged on an unprecedented halogen atom transfer Ueno-Stork cyclization of an O-allyl a,a-dihalohemiacetal acetate, catalyzed by the redox complex CuCl/N,N,N 0 ,N 00 ,N 00pentamethyldiethylenetriamine.

A sediment sampling based on a two-dimensional mapping was performed in the harbour of Trieste (northern Adriatic Sea), considering 28 sites exposed to pollutant inputs from harbour and industrial activities. Polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) were determined in surface sediments, because these very persistent pollutants seem to be responsible for the depletion of benthic populations observed in this area. The correlation matrix indicates that PAHs and PCBs are non-correlated, and probably have different sources. Both cluster analysis performed on the sampling sites and graphical drawing of the PAH sediment contents make it possible to locate along the shoreline a band of more polluted sediments, clustered around a site facing a steelmaking factory, to be considered as the main source point for PAHs. The evaluation of phenanthrene to anthracene (P/AN) and¯uoranthene to pyrene (FL/PY) ratios permits the assessment of the pyrolytic, industrial origin of these PAHs, rejecting a second possible source of hydrocarbons (i.e., an oilpipeline terminal, situated near the steelmaking factory). Graphical drawing of the total PCB iso-concentrations reveals a different source-point for this other category of very persistent pollutants.

The OECD has proposed five principles for validation of QSAR models used for regulatory purposes. Here we present a case study investigating how these principles can be applied to models based on Kohonen and counter propagation neural networks. The study is based on a counter propagation network model that has been built using toxicity data in fish fathead

Cadmium and zinc concentrations were determined in hepatopancreatic tissues of Mytilus galloprovincialis, reared in three non-contaminated hatcheries of the Gulf of Trieste (Northern Adriatic Sea). Mussels were collected in 13 sampling exits with monthly frequency for verifying possible seasonal variations. Freeze dried hepatopancreatic tissues were dissolved by nitric acid procedure using a microwave system; analysis of Zn and Cd followed by AAS technique.