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PubMed2002

Asymmetric cyclopentannelation: camphor-derived auxiliary.

The scope of an enantioselective cyclopentannelation reaction that makes use of allenyl ether-derived nucleophiles has been probed. The enantioselectivity is induced by a traceless chiral auxiliary that is easily derived from camphor. It has been shown that for gamma-substituted allene ethers that are axially chiral, very high enantiomeric excesses of cyclopentenone products are observed in the matched cases. Two fundamentally different mechanisms are observed, one for the cyclizations of allenyl ketones (see eq 7), the other for the cyclizations of allenyl alcohols (see eq 11). The methodology is versatile, efficient, and well-suited for applications in synthesis.

Allyl Compounds↗
PubMed2002

Highly enantioselective darzens reaction of a camphor-derived sulfonium amide to give glycidic amides and their applications in synthesis.

The reaction of an amide-stabilized sulfonium ylide bearing chiral groups on sulfur has been investigated. We have discovered that the camphor-derived amide-stabilized ylide reacts with aldehydes at -50 degrees C in ethanol to give glycidic amides in one step with up to 99% ee and complete diastereoselectivity. From analyzing reactions of different ratios of diastereomers at sulfur it was found that the major diastereomer gave very high enantioselectivity, while the minor one gave much lower selectivity (54% ee). Further mechanistic studies have revealed that enantioselectivity is controlled not in the betaine-forming step (C-C bond formation is reversible) but in the different barriers to bond rotation around the newly formed C-C of the two diastereomeric betaines. Further transformations of epoxyamides were investigated. It was found that epoxyamides could be converted into epoxyketones by reaction with organolithium reagents and that they could be ring-opened by nucleophiles with complete regioselectivity using Yb(OTf)3. The practicality of the process has been exemplified in the synthesis of SK&F 104353, a leukotriene D4 antagonist in the potential treatment of bronchial asthma.

Amides↗
PubMed2006

Highly enantioselective synthesis of glycidic amides using camphor-derived sulfonium salts. Mechanism and applications in synthesis.

The reactions of a range of amide-stabilized sulfur ylides derived from readily available camphor-derived sulfonium salts for the synthesis of glycidic amides have been studied. Primary, secondary, and tertiary amides were tested, and it was found that the highest enantioselectivities were observed with tertiary amides, which provided glycidic amides in good to excellent yields, exclusive trans selectivity, and excellent enantioselectivities. The reaction was general for aromatic aldehydes, but aliphatic aldehydes gave more variable enantioselectivities. The epoxy amides could be converted cleanly into epoxy ketones by treatment with organolithium reagents. We were also able to effect selective ring opening of the epoxy amides with a variety of nucleophiles, followed by hydrolysis of the amide to yield the corresponding carboxylic acid. This methodology was applied to the total synthesis of the target compound SK&F 104353. A combination of crossover experiments and theoretical calculations has revealed that the rate- and selectivity-determining step is ring closure, not betaine formation as was the case for phenyl-stabilized ylides.

Amides↗
PubMed2001

Solution structures of the mixed aggregates derived from lithium acetylides and a camphor-derived amino alkoxide.

Low-temperature (6)Li, (13)C, and (15)N NMR spectroscopies reveal that mixtures of lithium cyclopropylacetylide or lithium phenylacetylide (RCCLi) and a vicinal amino alkoxide derived from camphor (R*OLi) in THF/pentane afford an asymmetric (RCCLi)(3)(R*OLi) mixed tetramer and a C(2)-symmetric (RCCLi)(2)(R*OLi)(2) mixed tetramer depending on the stoichiometries. The corresponding (RCCLi)(R*OLi)(3) mixed tetramer is not observed. R*OLi-mediated additions of PhCCLi to benzaldehyde proceed with up to an 8:1 enantiomeric ratio that depend on both the choice of R*OLi and the PhCCLi/R*OLi stoichiometries. The results are considered in light of a previously proposed mechanism for the 1,2-addition to a trifluoromethyl ketone.

Camphor↗
PubMed2002

Chiral tricyclic iminolactone derived from (1R)-(+)-camphor as a glycine equivalent for the asymmetric synthesis of alpha-amino acids.

The development of a highly efficient and stereoselective methodology for the preparation of alpha-amino acids is described. The chiral template, tricyclic iminolactone 7, was synthesized from (1R)-(+)-camphor in five steps in 50% overall yield. Alkylation of iminolactone 7 afforded the alpha-monosubstituted products in good yields (74-96%) and excellent diastereoselectivities (>98%). Hydrolysis of the alkylated iminolactones furnished the desired alpha-amino acids in good yields and enantioselectivities with nearly quantitative recovery of the chiral auxiliary 4.

Alanine↗
PubMed2002

Asymmetric electrophilic amination of various carbon nucleophiles with enantiomerically pure chiral N-h oxaziridines derived from camphor and fenchone.

The first two stable enantiomerically pure chiral N-H oxaziridines, derived from camphor and fenchone, are shown to act as electrophilic sources of nitrogen upon reaction with various carbon nucleophiles. Nitrogen is transferred, together with the camphor/fenchone unit, when deprotonated esters, malonates, and nitriles are used as nucleophiles. One of the ester or nitrile units in the substrate usually undergoes hydrolysis; a cyclic mechanism is proposed to account for this observation.

Amination↗
PubMed2006

Fenchone, camphor, 2-methylenefenchone and 2-methylenecamphor: a vibrational circular dichroism study.

We report and discuss the infrared (IR) vibrational circular dichroism (VCD) spectra of the enantiomeric pairs of the olefin derivatives of fenchone (1,3,3-trimethyl-2-methylenebicyclo[2.2.1]heptane) and camphor (1,7,7-trimethyl-2-methylenebicyclo[2.2.1]heptane), respectively, together with those of the parent molecules. The VCD spectra were taken in three spectral regions: the mid-IR region, encompassing the fundamental deformation modes, the region of CH-stretching fundamental modes and the NIR-region between 1100 and 1300 nm, which corresponds to the second CH-stretching overtone. The VCD and absorption spectra in the first two regions are analyzed by use of current density functional theory (DFT) calculations. The NIR region is analyzed by a protocol that consists of the use of DFT-based calculations and in assuming local mode behavior: the local mode approach is found appropriate for interpreting the absorption spectra and, for the moment, acceptable for calculating NIR-VCD spectra. The analysis of the first region allows us to track the contribution of the C=O group in the vibrational optical activity of C-C stretching modes; notable differences are indeed found in olefins and ketones. On the contrary, in the other two regions the VCD spectra of olefins and ketones are more similar: in the normal mode region of CH stretching fundamentals the spectra are determined by the mutual orientation of the CH bonds; in the second overtone local mode region olefins and ketones signals show some differences.

Camphanes↗
PubMed2005

Unusual cyclopropanation of 9-bromocamphor derivatives: a novel formal C(1)-C(7) bond cleavage of camphor.

[reaction: see text] An unusual cyclopropanation of 9-bromocamphor derivatives 1 to a 7-spiro-cyclopropyl camphor derivative 3 was effected by the action of potassium tert-butoxide (or sodium hydride) in warm DMSO. The exo-hydroxy group and a non-hydrogen endo-substituent at C(2) have proven to be essential structural elements, and the solvent DMSO has proven to be the sole effective reaction medium. Tricyclic compound 3 undergoes a facile tandem Wagner-Meerwein rearrangement-cyclopropyl ring-opening under mild acidic conditions, leading to norbornenyl derivative 12 and subsequent Meinwald rearrangement of bicyclic epoxide 13 to a formal C(1)-C(7) bond cleavage product 14.

Camphor↗
PubMed2003

On the impossibility of determination of stepwise binding constants for the 1 : 2 complex of (+)-camphor with alpha-cyclodextrin.

Knowledge of stepwise binding constants for complexes with higher than 1:1 stoichiometry would allow one to study the cooperativity of their formation. However, a detailed analysis of partitioning of the overall binding constant beta 12 determined by NMR titrations for the 1:2 complex of (+)-camphor with alpha-cyclodextrin into the stepwise ones K1 and K2 carried out analogously to published procedures revealed that the partitioning cannot be carried out unequivocally for K1 << K2. The programs for partitioning cannot be used as a black box and a satisfactory reproduction of the experimental dependence of relative shifts as a function of relative CD concentration should not be the only criterion of the reliability of the stepwise binding constants obtained using such programs.

Camphor↗
PubMed2005

[Efficacy and safety of a herbal drug containing hawthorn berries and D-camphor in hypotension and orthostatic circulatory disorders/results of a retrospective epidemiologic cohort study].

BACKGROUND AND OBJECTIVE: Korodin Herz-Kreislauf-Tropfen, a herbal drug containing D-camphor (CAS 76-22-2; 2.5 %) and a liquid extract of fresh hawthorn berries (97.3%), has been used since many years for the treatment of orthostatic hypotension. The combination as well as its constituents were tested in clinical trials against placebo with healthy volunteers and patients using tilt-tests. The objective of this study was to investigate efficacy and safety of the drug under the conditions of medical practice in comparison to other drugs admitted for this indication. PATIENTS AND METHODS: The study was performed as an epidemiological retrospective cohort study in 46 medical practices in Germany. In the practices the files were reviewed for patients who were treated between 1st January 2000 and 31st December 2002 for orthostatic hypotension. Included in the study were all patients who were treated either with the test drug or a control drug containing etilefrine, oxilofrine, midodrine, norfenefrine or dihydroergotamine and who met the inclusion criteria. The data of the files were coded, transferred to case report forms and augmented by the physician's statements about symptoms and success. Effect criteria were the improvement of symptoms and change of blood pressure during treatment. The correctness of the data was controlled using anonymous copies of the files. A total of 490 patients (399 in the test-group and 91 in the control group) between 11 and 102 years were included in the study. To correct heterogeneities in baseline conditions, treatment results were adjusted by regression and stratification to equal baseline conditions using the propensity score. RESULTS: The adjusted odds ratio for improvement was 5.6, the adjusted mean increase of the systolic blood pressure the 2-fold compared to the control group. The difference was highly significant and did not depend on age or initial blood pressure. In the test group two adverse events were observed which had no relation to the medication; in the control group one reversible event with a probable relation to the medication was observed. CONCLUSIONS: The test drug was proven as effective and safe in the treatment of orthostatic hypotension in medical practice for all age groups and independent of the initial blood pressures.

Adult↗
PubMed2006

Theoretical study on the circular dichroism in core and valence photoelectron angular distributions of camphor enantiomers.

In the present work the photoelectron circular dichroism of camphor has been theoretically studied using B-spline and continuum multiple scattering-Xalpha methods, and comparisons are made with available experimental data. In general, rather large dichroism effects have been found for both valence and core (O 1s, C 1s) photoionizations. The agreement between the two calculations reported here and previous experimental measurements for core C 1s data is essentially quantitative. For valence ionization satisfactory agreement between theory and experiment has been obtained and the discrepancies have been attributed to both exchange-correlation potential limitations and the absence of response effects in the adopted formalism. The calculations predict, moreover, important features in the cross-section profiles, which have been discussed in terms of dipole-prepared continuum orbitals.

Camphor↗
PubMed1969

Approximation of rotational strengths from molar rotation data and generation of rotatory dispersion curves for d-camphor-10-sulfonate.

Starting with the expression for optical rotatory dispersion in the absorption region that was arrived at by Condon, two series were considered for the purpose of achieving the experimentally observed, steeper wavelength dependence in the absorption region while retaining the established 1/lambda(2) law in regions removed from absorption. The first two terms of one series in which the second term exhibits a 1/lambda(6) wavelength dependence were found to calculate satisfactorily the optical rotatory dispersion curve of d-camphor-10-sulfonate from 400 mmu to 190 mmu when only three bands were considered. Evaluated at the extrema, the two-term expression can be approximated by a simple equation which allows calculation of the rotational strength of a nonoverlapping band by using only the wavelength and molar rotation of the extrema and the index of refraction of the solution. The rotational strengths calculated from optical rotatory dispersion data in this manner closely agree with those calculated from corresponding circular dichroism data. Thus when position and magnitude of rotatory dispersion extrema alone are reported for carbonyls, it is suggested that such published data may be converted to approximate rotational strengths.

Camphor↗
PubMed1974

Fusion and compatibility of camphor and octane plasmids in Pseudomonas.

The octane (OCT) plasmid in Pseudomonas putida derived from the omega-hydroxylase-carrying strain of Coon and coworkers is transferable to the camphor (CAM) plasmid-bearing strain by conjugation or by transduction. While the majority of the Cam (+)Oct(+) exconjugants segregate Cam(+) or Oct(+) cells, exconjugants with stable Cam (+)Oct(+) phenotype (CAM-OCT) can be detected at a low frequency. The transductants are all of the CAM-OCT phenotype. In the stable Cam (+)Oct(+) strains, the OCT plasmid resembles the CAM plasmid with respect to curing by mitomycin C, transfer in conjugation, and reaction to ts (temperature-sensitive) mutation specifically affecting CAM plasmid replication. Therefore, it is suggested that certain regions of homology exist between the CAM and OCT plasmids that enable them to recombine to form a single plasmid, and to overcome the incompatibility barrier that prevents their coexisting.

Alkanes↗
PubMed1976

A thermodynamic model of regulation: modulation of redox equilibria in camphor monoxygenase.

Regulation of biological phenomena occurs in all types of systems, being manifested in many different reaction types, from allosteric behavior in proteins, through modulation in energy and information transfer, to the control of growth and differentiation in cells, organelles, and organisms. In this communication, a modulation in oxidation/reduction potential via ligation of substrate and protein components in the camphor 5-exo-monoxygenase system is described in terms of a four-state system using as fundamental parameters the transition free energies between equilibrium states. This approach provides a concise description of the data and is useful for describing many aspects of regulatory phenomena.

Camphor↗
PubMed2006

The ultraviolet filter 3-benzylidene camphor adversely affects reproduction in fathead minnow (Pimephales promelas).

The ultraviolet (UV) filter 3-benzylidene camphor (3BC) is used in personal care products and in a number of materials for UV protection. 3BC has been shown in vitro and in vivo in fish to be estrogenic, but possible effects on fertility and reproduction are unknown. In this study we evaluate whether 3BC affects reproduction of fish Pimephales promelas. After a preexposure period of 21 days, reproductively mature fathead minnows were exposed to increasing concentrations of 3BC for 21 days in a static-renewal procedure. Actual 3BC concentrations decreased to 23% of initial levels and median concentrations were 0.5, 3, 33, 74, and 285 microg/l. 3BC affected reproduction in a dose-dependent manner with weak effects on fecundity at 3 microg/l, a significant decrease at 74 microg/l, and a cessation of reproduction at 285 microg/l. 3BC was accumulated in fish with an average bioconcentration factor of 313 +/- 151. Dose-dependent demasculinization in secondary sex characteristics of male fish and dose-dependent induction of plasma vitellogenin occurred, which was significant at 74 microg/l and higher. 3BC had a profound and dose-dependent effect on the histology of gonads of male and female fish at 3 microg/l and higher. At 74 and 285 microg/l, oocyte and spermatocyte development was inhibited in male and female gonads. Testes of exposed males had much fewer spermatogenic cysts, and ovaries of exposed females had much fewer mature but more atretic, follicles. This study shows significant effects of the UV filter 3BC on fertility, gonadal development, and reproduction of fish after short-term exposure that may have negative consequences on the population level.

Animals↗
PubMed2002

Effects of parachlorophenol and camphorated parachlorophenol on the phagocytic activities of a murine macrophage cell line (RAW264.7).

The aim of this study was to determine whether the phagocytic functions of a murine macrophage cell line (RAW264.7 cells) may be altered by parachlorophenol (PCP) and camphorated parachlorophenol (CMCP). The adherence capacities of PCP- or CMCP-treated cells on plastic surfaces were much lower than those of untreated cells. When the PCP- or CMCP-treated cells were incubated with Actinobacillus actinomycetemcomitans, phagocytosis of these cells was significantly reduced in a dose-dependent fashion compared with that of untreated cells. Preactivation with bacterial lipopolysaccharide on PCP- or CMCP-treated cells failed to completely restore the phagocytosis of this periodontopathogen. The phagocytic functions of PCP- or CMCP-treated cells to this periodontopathogen opsonized with anti-A. actinomycetemcomitans were also reduced compared with those of untreated cells but were comparable with those of untreated cells incubated with unopsonized bacteria. The results of this study indicated, therefore, that both PCP and CMCP may, indeed, reduce the phagocytic activities of murine macrophages.

Aggregatibacter actinomycetemcomitans↗