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PubMed1996

Highly Stereocontrolled Cyclopropanation by the 1,3-Elimination of a Bis(tributylstannyl)propanol Derivative.

The highly stereoselective ring closure of gamma-hydroxystannyl derivative was realized. The aldol reaction of methyl bis(tributylstannyl)propionate (2) with aldehyde 5 proceeds stereoselectively to give (gamma-hydroxypropyl)stannane 6, and the cyclopropanation reaction of aldol product 6 proceeds smoothly in a highly stereoselective manner presumably via a W-shape transition state. The stannyl group on the cyclopropane ring can be converted into various electrophiles with a retention of configuration. As a result, various stereocontrolled 1,2,3-trisubstituted cyclopropanes can be obtained in high yields.

Journal Article↗
PubMed1997

Cyclopropanation with Diazomethane and Bis(oxazoline)palladium(II) Complexes.

Studies toward the development of an enantioselective diazomethane-based cyclopropanation reagent derived from bis(oxazoline)palladium(II) complexes are reported. Several simple palladium chelates, 2 and 7, in addition to the novel carbon-bound complexes 15 were synthesized and evaluated in the cyclopropanation of various electron-deficient olefins. The X-ray crystal structure of aryl-bis(oxazoline)palladium complex 15c is described. Although all catalysts efficiently affected cyclopropanation, all products were racemic. An intriguing relationship between substitution on the oxazoline ring, particularly the commonly-derivatized 4-position, and catalyst efficiency was discovered. The results are rationalized by either partial or complete bis(oxazoline) decomplexation during the course of the reaction.

Journal Article↗
PubMed2002

Theoretical analysis of the reaction pathway and the effect of the axial ligand for 3-oxobutylideneaminatocobalt(II)-catalyzed cyclopropanation.

[structure: see text] The reaction pathway of the cyclopropanation catalyzed by the 3-oxobutylideneaminatocobalt(II) complex was analyzed by the density functional method to reveal that the axial donor ligand produced two prominent effects. One is that the activation energy for the formation of the cobalt carbene complex was reduced and that the activation energy for the cyclopropanation step was increased. The other is that the distance of the carbene carbon above the ligand plane was shortened during the cyclopropanation step.

Journal Article↗
PubMed2002

Novel intramolecular cyclopropanation reaction of unsaturated beta-keto esters.

[reaction: see text] Fused cyclopropane beta-keto esters are versatile intermediates for the synthesis of many biologically active natural products. Here we report a new intramolecular cyclopropanation reaction of unsaturated beta-keto esters. In the presence of I(2), Et(3)N, and Lewis acids such as Mg(ClO(4))(2) and Yb(OTf)(3), beta-keto esters 1 bearing various olefin substituents were transformed to fused cyclopropanes 2 in a highly stereospecific manner with moderate to good yields. The mechanism of the reaction was also investigated.

Journal Article↗
PubMed2004

Rh(II)-catalyzed enantioselective cyclopropanation of olefins with dimethyl malonate via in situ generated phenyliodonium ylide.

Olefins are cyclopropanated with dimethyl malonate (1a) iodosylbenzene (PhI=O) and a Rh(II) carboxylate catalyst via an in situ generated phenyliodonium ylide (1c). Enantioselectivities of up to 90% for 4-bromostyrene and 98% for pent-1-ene have been observed with (S)-N-4-bromo-1,8-naphthanoyl-tert-leucine (4c) as the chiral ligand. The same catalyst was effective for olefin cyclopropanation with Meldrum's acid, giving cyclopropanes with 96% (with styrene) and 87% ee (with pent-1-ene), respectively.

Journal Article↗
PubMed2006

Synthesis and cross-coupling reactions of 7-azaindoles via a new donor-acceptor cyclopropane.

[reaction: see text] A new type of donor-acceptor cyclopropane has been prepared from commercially available cyclopropane-1,1-diesters. This cyclopropane reacts with triflic anhydride to produce an isolable tristrifloxy intermediate which when treated with primary amines gives 6-trifloxy-7-azaindolines which in turn can be dehydrogenated to the azaindoles. The 6-trifloxy substituent can be used to introduce diversity at this position via a variety of cross-coupling reactions thus preparing potentially interesting compounds based on the important 7-azaindole pharmacophore.

Journal Article↗
PubMed2006

High-resolution infrared spectroscopy and ab initio studies of the cyclopropane-carbon dioxide interaction.

A jet-cooled high-resolution infrared spectrum of the cyclopropane-carbon dioxide complex was detected for the first time, using a rapid scan infrared spectrometer with an astigmatic multipass sample cell. The spectrum was recorded in the vicinity of the CO2 asymmetric stretching band (nu3) and exhibits a b-dipole selection rule. Altogether, over 200 lines were observed, assigned, and fitted to Watson's S-reduction Hamiltonian. Rotational and quartic distortion constants were obtained. The band origin was located at 2347.6263(2) cm(-1), redshifted by 1.5230(2) cm(-1) from the corresponding frequency of the CO2 monomer. The experimentally determined structure shows that CO2 lies next to a C-C bond edge and is perpendicular to the C3 ring, indicating that the interaction is characterized by the bonding between the carbon atom of CO2 and the pseudo-pi system of cyclopropane. The intermolecular distance between the carbon atom of CO2 and the center of mass of cyclopropane was determined to be 3.667(2) A. Complete ab initio geometry optimizations and harmonic frequency calculations were carried out at the level of second-order Moller-Plesset perturbation theory with four different basis sets: cc-pVDZ, 6-311++G(d,p), aug-cc-pVDZ, and aug-cc-pVTZ. The lowest-energy structure identified with the three larger basis sets is in accord with the experimental finding. In addition, a transition state was identified and the tunneling barrier height was computed.

Journal Article↗
PubMed1972

Cyclopropane Fatty acids in relation to earliness in spring and drought tolerance in plants.

Long chain cyclopropane fatty acids were observed in the sulfolipid fraction extracted from leaves of the early spring plants Galanthus nivalis L. and Anthriscus silvestris L. (Hoffm.). The content of cyclopropane fatty acids with 25 carbon atoms appeared to be clearly correlated with earliness in spring, and it ranged from 68% (G. nivalis L., snow drop) to 0.5% (wheat). Several long chain cyclopropane fatty acids were found in the drought-tolerant Corynephorus canescens (L.) P.B., exclusively in the phosphatidyl choline fraction.

Journal Article↗
PubMed2005

Synthesis and HPLC enantioseparation of the cyclopropane analogue of valine (c3Val).

A new and efficient method is presented for the preparation of the N-Boc-protected cyclopropane analogue of valine, 1-(N-tert-butoxycarbonyl)amino-2,2-dimethylcyclopropanecarboxylic acid, both in racemic and enantiomerically pure forms. Cyclopropanation of the exocyclic double bond of 2-phenyl-4-isopropylidene-5(4H)-oxazolone with diazomethane followed by elaboration of the heterocyclic moiety provided multigram quantities of the racemic target compound. Subsequent HPLC resolution of a racemic precursor on a noncommercial chiral stationary phase has given access to enantiomerically pure products. Almost 1.5 g of the first-eluted enantiomer and 1.0 g of the second-eluted enantiomer have been isolated in optically pure form using a 150 x 20 mm ID column containing mixed 10-undecenoate/3,5-dimethylphenylcarbamate of cellulose covalently bonded to allylsilica gel with a mixture of hexanes/tert-butyl methyl ether/ethyl acetate as the mobile phase.

Chromatography, High Pressure Liquid↗
PubMedDate not supplied

[Synthesis and antitumor activity of cyclopropane derivatives of betulinic and betulonic acids].

New cyclopropane derivatives of betulin were synthesized by attachment of dichlorocarbenes or dibromocarbenes to the double bond of betulin diacetate, followed by the deprotection of hydroxyl groups. The betulin cyclopropane derivative was obtained from 20,29-dihydro-20,29-dichloromethylenebetulin by treatment with lithium in tert-butanol. These compounds were converted into the corresponding derivatives of betulonic acid by oxidation with chromium trioxide. The reduction of oxo group with sodium borohydride led to the corresponding derivatives of betulinic acid. 20,29-Dihydro-20,29-dichloromethylenebetulinic acid proved to be the most cytotoxic toward human melanoma of the Colo 38 and Bro lines and human ovarian carcinoma of the CaOv line (IC50 10 microM). 20,29-Dihydro-20,29-dibromomethylenebetulinic acid inhibited the growth of the Bro melanoma cell line and the CaOv carcinoma cell line practically by 50% at a concentration of 10 microM. The other derivatives of betulinic and betulonic acids were active toward all of the three cancer cell lines at concentrations higher than 10 microM. The English version of the paper: Russian Journal of Bioorganic Chemistry, 2005, vol. 31, no. 3; see also http://www.maik.ru.

Antineoplastic Agents↗
PubMed1981

Phase transition behaviour of artificial liposomes composed of phosphatidylcholines acylated with cyclopropane fatty acids.

Phase transitions of liposomes composed of synthetic phoshatidylcholines acylated with the cyclopropane fatty acids, lactobacillic and dihydrosterculic acid, were studied by differential scanning calorimetry. Transition temperatures were approx. 16 degrees C higher than for phosphatidylcholines acylated with the corresponding unsaturated fatty acids, cis-vaccenic and oleic acid. Though our transition temperatures were all several degrees lower than those determined by Silvius and McElhaney ((1979) Chem. Phys. Lipids 25, 125--134), the increase produced by replacement of the double bond with a cyclopropane ring was the same. We propose that this replacement, through its effect on membrane fluidity, may serve to regulate the activity of membrane-associated processes such as transport.

Acylation↗
PubMed1960

The kinetics of distribution of the fat-soluble inert gas cyclopropane in the body.

A kinetic analysis is made of the experimentally measured time course of respiratory uptake of the highly fat-soluble, inert gas cyclopropane by normal human subjects. The analysis is based on the well-known perfusion-limited model in which a number of body compartments are arranged in parallel with the lungs via the circulating blood. Three distinct body compartments are derived from the data. These are tentatively identified as: (a) adipose tissue (b) fat-poor tissue of low perfusion such as resting muscle, skin, and connective tissue (c) fat-poor tissue of high perfusion such as brain, heart, gut, liver, and kidney. Blood flow rates to the several compartments are also derived from the data. The rates to compartments (a) and (b) are each approximately 10 per cent of the estimated total cardiac output. The derived perfusion (blood flow rate/compartment weight) of the three compartments are in the range, respectively, (a) 2 to 4, (b) 1 to 2.5, (c) 25 to 75 ml/min/100 gm. Uncertainties arising from the experimental data and from simplifications of the model (neglect of lung fill-up phase of uptake and gross diffusion of cyclopropane from one tissue into another) are discussed. The present type of uptake experiment is significant for the problems of total body fat determination, of gross body composition in relation to weight change, of gross shunting of blood flow from one compartment to another, of anesthesia by fat-soluble substances, and of decompression sickness.

Adipose Tissue↗
PubMed2000

Inhibition of apple 1-aminocyclopropane-1-carboxylic acid oxidase, by cyclopropane-1,1-dicarboxylic acid and trans-2-phenylcyclopropane-1-carboxylic acid.

Cyclopropane-1,1-dicarboxylic acid (CDA) and trans-2-phenylcyclopropane-1-carboxylic acid (PCCA) are the main representatives of a group of compounds that are structural analogues of 1-aminocyclopropane-1-carboxylic acid (ACC) and have been proved to have an inhibitory effect on the wound ethylene produced by Lycopersicum esculentum fruit discs. During the experiments, that were carried out in this work the inhibition pattern of PCCA and CDA were studied when tested on partially purified apple ACO and their Ki values were determined. A mechanistic proposal was given, in order to explain the kinetic behaviour of the inhibitors. The common feature of these molecules is their cyclopropane ring, with different substitutes mainly at the positions C1 and C2. Two other compounds with similar structure where also tested as inhibitors, in order to clarify the relationship between structure and activity. These compounds are: 2-methyl cyclopropanecarboxylic acid (MCA), and cyclopropanecarboxylic acid (CCA).

Amino Acid Oxidoreductases↗
PubMed1998

Kinetic characterization of the inactivation of ammonia monooxygenase in Nitrosomonas europaea by alkyne, aniline and cyclopropane derivatives.

The kinetic mechanisms of seven inactivators of ammonia oxidation activity in cells of the nitrifying bacterium, Nitrosomonas europaea were investigated. The effects of the inactivators were specific for ammonia monooxygenase (AMO) which oxidizes ammonia to hydroxylamine. The aniline derivatives, 1,3-phenylenediamine and p-anisidine, were potent inactivators of AMO while other derivatives were ineffective as inactivators. Two cyclopropane derivatives, 1, 2-dimethylcyclopropane and cyclopropyl bromide, were inactivators while cyclopropane was not an inactivator. The mechanisms of three alkynes, 1-hexyne, 3-hexyne, and acetylene, were also examined. For all seven compounds, the inactivation of AMO was irreversible, time-dependent, first-order, and dependent on catalytic turnover. Saturation of the rate of inactivation was indicated for p-anisidine (kinact=2.85 min-1; KI=1.0 mM) and cyclopropyl bromide (kinact=4.4 min-1; KI=97 microM), but not for any of the remaining five inactivators, including acetylene. Ammonia slowed the rate of inactivation for acetylene and cyclopropyl bromide, but enhanced the rate of inactivation for the remaining inactivators. All seven compounds appear to be mechanism-based inactivators of AMO.

Ammonia↗
PubMed1979

Cyclopropane fatty acid synthase of Escherichia coli. Stabilization, purification, and interaction with phospholipid vesicles.

The cyclopropane fatty acid (CFA) synthase of Escherichia coli catalyzes the methylenation of the unsaturated moieties of phospholipids in a phospholipid bilayer. The methylene donor is S-adenosyl-L-methionine. The enzyme is loosely associated with the inner membrane of the bacterium and binds to and is stabilized by phospholipid vesicles. The enzyme has been purified over 500-fold by flotation with phospholipid vesicles and appears to be a monomeric protein having a molecular weight of about 90 000. The enzyme binds only to vesicles of phospholipids which contain either unsaturated or cyclopropane fatty acid moieties. CFA synthase is active on phosphatidylglycerol, phosphatidylethanolamine, and cardiolipin, the major phospholipids of E. coli, and also has some activity on phosphatidylcholine. The enzyme is equally active on phospholipid vesicles in the ordered or the disordered states of the lipid phase transition. Studies with a reagent that reacts only with the phosphatidylethanolamine molecules of the outer leaflet of a phospholipid bilayer indicate that CFA synthase reacts with phosphatidylethanolamine molecules of both the outer and the inner leaflets of phospholipid vesicles.

Cyclopropanes↗
PubMed2002

First evidence for the formation of a geminal dizinc carbenoid: a highly stereoselective synthesis of 1,2,3-substituted cyclopropanes.

Significant amounts of novel gem-dizinc carbenoids (RZnCHIZnR) are formed when diethylzinc is mixed with iodoform in CH2Cl2 at 0 degrees C. This reagent was shown to be effective in the cyclopropanation of butenediol derivatives to generate a cyclopropylzinc intermediate that could be trapped with a variety of electrophiles. 1,2,3-Substituted cyclopropane derivatives are formed with excellent diastereoselectivities by using this simple procedure.

Cyclopropanes↗