A revision of the brassoline genus Catoblepia (Lepidoptera: Rhopalocera)

The brassoline genus Catoblepia is revised: eight new subspecies are described, nine new synonymies established, the status of four species and subspecies is revised, one species ( singularis ) is returned to the genus Opsiphanes and ten lectotypes are designated. All known holotypes (20) and lectotypes (10) are figured, many for the first time. The refined taxonomy reveals an interesting pairing of the Andean subspecies of xanthicles and berecynthia and it is suggested that diese may be mimetic pairs. There is close agreement in the distribution of the Andean species and subspecies with die endemic centres previously recognized; east of the Andes, however, diere is no close correspondence and each of the subspecies has, in general, a distribution across several endemic centres.     

Differentiating manool and 13-epimanool with NMR chiral shift reagents

Use of NMR chiral shift reagents showed that a compound isolated from Pinus contorta bark and Tsuga heterophylla wood was 13-epimanool. Southern pine (Pinus spp.) tall oil contained a mixture of manool and 13-epimanool.     

Role of planktonic bacteria in productivity and cycling of organic matter in the Eastern Pacific Ocean

Total number, biomass, production, and respiration of bacterioplankton were measured in oligotrophic, mesotrophic and eutrophic waters of the Eastern Pacific. Total number of bacteria in the upper mixed layer and in the upper thermocline boundary layers varied from 30–60.10³ ml^-1 in oligotrophic waters to 100–400.10³ ml^-1 in mesotrophic waters of fronts and divergences, and to 1–2,5.10⁶ ml^-1 in eutrophic waters of coastal upwellings. Wet biomass varied from 5–10 mg l^-1 in oligotrophic waters, to 50–200 mg l^-1 in mesotrophic waters, and to 1–2 g m^-3 in eutrophic waters. Below the layer of maximum temperature gradient i.e. below 35–50 m, bacterioplankton density decreased 5–10 times. P/B coefficients per day were highest in the oligotrophic surface water ( 1), and lowest in the eutrophic ones (0.2–0.4). In mesotrophic waters they were intermediate (0.4–1.0). the stock of labile organic matter (LOM) accessible to microbial action varied from 0.3 to 1.6 mg Cl^-1. Its highest value occurred in the upwelling area. The stock of LOM does not noticeably decrease from the euphotic zone to a depth of 2 000 m. Its turnover time varied from 5 to 45 days in surface waters, and 30–50 years in deep oceanic waters. The role of bacterioplankton in productivity and in cycling of organic matter in surface — and deep oceanic waters is discussed.     

A molecular dynamics investigation of chiral discrimination complexes as chiral stationary-phase models: Methyl N-(2-naphthyl)alaninate with N-(3,5-dinitrobenzoyl)leucine n-propylamide

Molecular dynamics simulations were performed on complexes of (S)-methyl N-(2-naphthyl)alaninate (NAP) with the enantiomers of N-(3,5-dinitrobenzoyl)leucine n-propylamide (DNB), which are used as models for chiral stationary-phase systems developed by Pirkle and co-workers. These studies were undertaken to qualitatively examine (pictorially) the role of entropic effects in these systems. The results of the dynamics calculations were used to refine the search for low-energy conformers. The structures were refined by the use of BioDesign's molecular mechanics method implemented in Biograf. The results of the structural refinements support our previous observation that the SR complex can achieve the same three primary interactions which are observed in the SS structure (i.e., two intermolecular hydrogen bonds and pi stacking) without a significant increase in energy. In addition, these primary interactions are conserved during molecular dynamics simulations with the occurrence of conformations which differ only in the rotational states of the alkyl side chains and ester group (which bears two potential hydrogen bond acceptors utilized in both the homo- and heterochiral complexes). The major difference in the two complexes is the relative position of the sec-butyl group and hydrogen atom on DNB's chiral center, both of which are outside the primary interaction region. All other local minima which have different relative pi orientations (“front–back,” “back–back,” and “back–front” as defined herein) are not sufficiently populated to make more than a negligible contribution to the statistical (time- or energy-averaged) analysis of the (SS)- and (SR)-NAP–DNB complexes. Thus the entropic effects observed in this study (e.g., alkyl side chain or ester group rotations) do not show evidence of qualitative differential effects on the maintenance of the same three primary interactions by both the homo- and heterochiral complexes. The reliability of the present study, which provides pictorial representations of the entropic effects, is not sufficient to determine whether the entropic effects observed herein are sufficient to achieve enantiomeric discrimination alone or in conjunction with other factors (e.g., conformational strain energy). Thus, all of the computational studies we have performed to date (i.e., our previous studies, which include strain energy and through-space field effects, and the present study, which includes entropic effects) show no evidence of any qualitative difference in the homo- and heterochiral complexes in terms of maintaining the same three “contact points”.     

The asymmetric hydroformylation in the synthesis of pharmaceuticals.

The asymmetric hydroformylation reaction represents a potential powerful synthetic tool for the preparation of large number of different chiral products to be used as precursors of several organic compounds endowed with therapeutic activity. Essential and nonessential amino acids, 2-arylpropanoic acids, aryloxypropyl- and beta-phenylpropylamines, modified beta-phenylethylamines, pheniramines, and other classes of pharmaceuticals are available through enantioselective oxo-reaction of appropriate functionalized olefins; this process is catalyzed by rhodium or platinum complexes with chiral ligands, mainly chelating phosphines, and sometimes affords very high enantiomeric excesses. Furthermore, the application of many simple optically active aldehydes arising from asymmetric hydroformylation as chiral building blocks for the synthesis of complex pharmacologically active molecules such as antibiotics, peptides, antitumor macrocycle compounds, and prostaglandins is conveniently emphasized. The possibility of a future application of this asymmetric process for the production of many synthons to obtain other valuable pharmaceuticals is widely discussed too.     

Excited chlorophyll and related problems

A historical outline is presented of the primary light energy conversion in photosynthesis studied by our research group. We found that photoexcited chlorophylls, pheophytins and porphyrins are capable of reversible and irreversible oxido-reduction. The mechanism of the photosensitized electron transfer from donor to acceptor molecule is based on the reversible photochemical oxido-reduction of the pigment-sensitizer. This property of the excited pigments is realized in the reaction centres of photosynthetic cells when photooxidation of bacteriochlorophyll(s) or chlorophyll of Photosystem II is coupled to pheophytin reduction leading to the final charge separation.The studies of the state and function of pigments in the course of chlorophyll biosynthesis in cellular and non-cellular systems revealed different monomeric and aggregated forms of pigments and the phenomenon of self-assembly of various forms of chlorophylls, bacteriochlorophylls and protochlorophylls. The discovery of protochlorophyll photoreduction in non-cellular system allowed the study of the molecular mechanisms of this reaction.In order to construct models of photosynthetic charge separation, we used inorganic photocatalysts-semiconductors, mainly titanium dioxide, and pigments incorporated into detergent micelles or lipid vesicles. To prevent back reactions we used heterogeneous systems where primary unstable products were spatially separated; coupling of solubilized chlorophylls or semiconductor particles with bacterial hydrogenase led to molecular hydrogen photoproduction. Light excitation of some coenzymes, mainly NADH and NADPH, was considered from the point of view of early events of chemical evolution.Now we are interested in the creation of photobiochemical systems using principles of photosynthesis for the conversion and storage of solar energy.Written at the invitation of Govindjee.     

Metabolism of halazepam by rat liver microsomes: stereoselective formation and N-dealkylation of 3-hydroxyhalazepam

Metabolism of halazepam [7-chloro-1,3-dihydro-5-phenyl-1-(2,2,2-trifluoroethyl)-2H-1,4-benzod iazepin- 2-one, HZ] was studied by incubation with liver microsomes prepared from untreated, phenobarbital (PB)-treated, and 3-methylcholanthrene (3MC)-treated male Sprague-Dawley rats. Metabolites of HZ were separated by normal-phase HPLC. Relative rates of HZ metabolism by liver microsomes prepared from untreated and treated rats were PB-treated much greater than untreated greater than 3MC-treated at low concentration of microsomal enzymes (0.25 mg protein per ml of incubation mixture) and PB-treated much greater than 3MC-treated approximately untreated at high concentration of microsomal enzymes (2 mg protein per ml of incubation mixture). The relative amounts of major metabolites were found to be 3-hydroxy-HZ (3-OH-HZ) greater than N-desalkylhalazepam (NDZ, also known as N-desmethyldiazepam and nordiazepam) much greater than oxazepam (OX) for all three rat liver microsomal preparations and the distribution of metabolites was independent of microsomal enzyme concentrations. Enantiomers of 3-OH-HZ were resolved by HPLC on a Chiralcel OC column (cellulose trisphenylcarbamate coated on silica gel, particle size 10 microns). 3-OH-HZ enantiomeres have racemization half-lives of approximately 150 min in pH 4, 7.5, and 10 aqueous solutions. 3-OH-HZ formed in the metabolism of HZ by liver microsomes prepared from untreated and treated rats were found to have 3R/3S enantiomer ratios of 37/63 (untreated), 55/45 (PB-treated), and 36/64 (3MC-treated), respectively. N-dealkylation of 3-OH-HZ by liver microsomes from PB-treated rats was substrate enantioselective; the 3R-enantiomer was N-dealkylated faster than 3S-enantiomer.(ABSTRACT TRUNCATED AT 250 WORDS)     

Glutathione conjugation and pharmacokinetics of 2-bromo-3-phenylpropionic acid in vitro and in the rat in vivo.

Glutathione (GSH) conjugation of the chiral compound 2-bromo-3-phenylpropionic acid (BPP) was studied in vitro and in the rat in vivo. GSH conjugation of BPP, catalyzed by a mixture of glutathione-S-transferases (GST's) from rat liver cytosol in vitro, was stereoselective: at a substrate concentration of 250 microM, (R)-BPP was more rapidly conjugated than (S)-BPP (R/S-ratio = 2.6). The blood elimination kinetics of the separate BPP enantiomers and the biliary excretion kinetics of the corresponding GSH conjugates were studied in the rat in vivo after administration of (R)- or (S)-BPP at a dose level of 50 mumol/kg. Elimination of (R)-BPP from blood was faster than that of (S)-BPP: half lives were 9 +/- 2 min for (R)-BPP and 13 +/- 1 min for (S)-BPP. The biliary excretion rate of the GSH conjugate of (R)-BPP declined monoexponentially, while that of the GSH conjugate of (S)-BPP displayed a biphasic profile. Half lives of excretion were 13 +/- 1 for the GSH conjugate of (R)-BPP, and 11 +/- 2 for the GSH conjugate of (S)-BPP (second phase). The first phase in the biliary excretion of the GSH conjugate of (S)-BPP could not be attributed to capacity limitation of biliary transport carriers as higher excretion rates were attained upon administration of higher doses (100 and 200 mumol/kg) of (S)-BPP). The blood elimination profiles of (R)- and (S)-BPP differed greatly from the biliary excretion profiles of the corresponding GSH conjugates. This suggests that the kinetics of BPP conjugate excretion are determined by other processes than hepatic GSH conjugation.     

Chromatographic optical resolution on trans-1,2-diaminocyclohexane derivatives: Theory and applications

An overall view on some new chiral stationary phases based on (trans)-1,2-diaminocyclohexane is illustrated. The selected chiral moiety, derivatized with different aroyl groups, has been linked to a silica matrix in order to give chiral stationary phases (CSPs) enabling them to be used efficiently in the normal and reverse phase, both for analytical and preparative purposes. In addition new polymeric CSPs have been prepared by using the same selector, suitably modified, as monomer. The new chiral stationary phases have been characterised by physicochemical methods and used for the resolution of various racemic compounds classes such as α-aryloxyacetic acids, alcohols, sulfoxides, selenoxides, phosphinates, tertiaryphosphine oxides, benzodiazepines etc. without prederivatization or as amines, amino acids, amino alcohols, nonsteroidal antiinflammatory agents in a derivatized form. The separated solutes structural variety suggests that multiple interaction sites are involved in the recognition process: some thermodynamic data relative to the CSPs—selectands interactions are also illustrated. © 1992 Wiley-Liss, Inc.     

Asymmetric synthesis polymerization of meso oxiranes and thiiranes

The asymmetric synthesis polymerization or “enantiogenic” polymerization of some meso oxiranes, cis-dimethyloxirane (cis-DMO) and cyclohexene oxide (CHO), and thiiranes, cis-dimethylthiirane (cis-DMT) and cyclohexene sulfide (CHS), initiated with different chiral systems was examined. Strong differences in behaviour were observed between oxiranes and thiiranes depending on the initiator used. The initiators based on ZnEt₂ or CdMe₂ and a chiral diol give optically active polymers from meso thiiranes but fail to induce an asymmetric polymer synthesis with meso oxiranes. A new chiral initiator based on ZnEt₂ and (1S,2R)-ephedrine allowed us to prepare optically active poly CHOs, which can be fractionated into fractions exhibiting opposite optical activities. © 1992 Wiley-Liss, Inc.