Shalom Sarel

Reactions of dicyclopropylacetylene with iron carbonyls

Abstract Dicyclopropylacetylene has been brought into reaction under photolytic conditions with Fe(CO) 5 and under thermal conditions with Fe 2 (CO) 9 and with Fe 3 (CO) 12 . It was possible to obtain primarily monoacetylene adducts or bis(acetylene) adducts by modification of the reaction conditions. In addition to products normally obtained from reactions of acetylenes with iron carbonyls, products derived from cyclopropane ring opening were important. Of particular interest are products which resulted from ring opening and carbonyl insertion to yield cyclopentenone derivatives. Experiments were attempted to show the interrelationships between the various products obtained.

In vitro effects of three iron chelators on mitogen-activated lymphocytes: Identification of differences in their mechanisms of action

The effects of three iron chelators (ADR-529/ICRF-187; omadine/pyrithione; and a newly synthesized pyridoxal-based iron chelator, SAG-15) on cultured BALB/c murine lymph node cells stimulated with phorbol myristate acetate and ionomycin have been investigated. All three agents were found to inhibit [3H]-thymidine incorporation after 66-72 h incubation. Pretreatment of ADR-529 and omadine with Fe(III) or Fe(II) ions did not prevent their inhibitory effects. However, pretreatment of SAG-15 with Fe(II) or Fe(III) ions led to a significant increase in the ID50. Time-course studies of cell viability and thymidine incorporation demonstrated that the inhibitory effect of omadine was attributable to cell killing while for ADR-529 and SAG-15 there were both cytostatic and cytotoxic effects. Cell cycle analysis showed that treatment of cells with ADR-529 led to arrest in G2/M while treatment with SAG-15 led to a G0/G1 arrest. Iron has an obligatory role in T-lymphocyte activation that may be related to the formation of reactive oxygen species. SAG-15 is a new iron chelator that will help in the elucidation of the precise role of iron in lymphoproliferation. Since SAG-15 is an extremely effective iron chelator in vivo it has potential as an immunosuppressive agent.

Prianicin A and B, nor-sesterterpenoid peroxide antibiotics from Red Sea sponges

The antibiotic properties of 2 acidic C24H40O4 nor-sesterterpenoid peroxides, prianicin A (1) and B (2), against gram-positive and gram-negative bacteria, and against fungi are herein described. They are 4–10 times more effective than tetracycline againstbeta hemolytic Streptococcus, but significantly non-effective against a variety of gram-negative bacteria.

The synthesis of hexacyclopropylbenzene via cyclotrimerization of dicyclopropylacetylene by Fe3(CO)12

Di-cyclopropyl-acetylen (I) reagiert in Gegenwart von Trieisen-dodecacarbonyl (II) zum Hexakis-cyclopropyl-benzol (III) neben dem Tetrakis-cyclopropylcyclopentadienon (IV) und zwei weiteren Eisen-Komplexen (V) und (VI).

The catalytic effect of catiohic amino micelles on the hydrolysis of substituted phenyl esters

Abstract The catalytic effects of two aminocationic micelles on the hydrolysis of substituted phenyldecanoate esters and a positively charched benzoate ester (CPNBA) were determined. The micellaric catalysts were of the general structure [CH3(CH2)3N(CH3)2(CH2)nNH2]Br where n=2 (micelle 1); n=3 (micelle 2). The kinetics followed the expression: kobs =ko+kcat x Ka/(Ka+H+)+koOH[OH-]. From the comparison of the kc OH rates with specific base catalysis rates deduced from reactions in non catalytic micelles, it was concluded that the kc OH term, is compatible mainly with an aminolysis reaction catalyzed by hydorxide ion. The Hammett and Bronsted correlations (p=2.8; β=1.0), in addition to the very small deuterium isotope effect, suggested that kcat corresponded with a nucleophilic mechanism. The Bronsted plot of log kcat vs pKa of the phenolate leaving groups in micelles 1 and 2 showed a biphasic behaviour. The break in the curve occured at pKo=5.89 and pKo=6.78 respectively. The partition ratio k±/k-a of the zwiterionic tetrahedral intermediate was derived from the experimental data and produced the following correlation: log k±/k-a=-0.92pKo+0.43pKN+2.466. The ester CPNBA exhibited a deuterium isotope effect of 2.1. From product analysis it was concluded that the reaction proceeds via a general base catalysis of aminolysis.

Trends in electron-impact fragmentation of substituted styrenebis(tricarbonyliron) complexes induced by the metal and substitution

Abstract A study of electron-impact induced processes of thirty substituted styrenebis(tricarbonyliron) complexes XC 6 H 4 C(R α )=CR β [Fe(CO) 3 ] 2 , and of some ten corresponding styrene free ligands is described. All the mass spectra of the organoiron complexes are characterized by the consecutive losses of carbon monoxide followed by loss of one or tow iron atoms: [LFe 2 (CO) 6 ] +. (a) LFe +. 2 (c) LFe +. (g) L + Depending on the nature of the substituent, X, and its position on the styrene ligand, the organic moiety in LFe + ruptures in four main modes: ( d ) loss of neutral methane when X = H, CH 3 , C 6 H 5 , CH 3 O and F; R α = CH 3 and R β = H; ( e ) loss of neutral acetylene when X = H, CH 3 O; R α = H and R β = CH 3 ; ( f ) loss of HX when X = halogen, R α = H, CH 3 and R β = H; ( g ) loss of iron. In the halogen-containing organoiron complexes, the ionic fragment LFe +. 2 predominates in the mass spectra. It is characterized by its tendency to lose a neutral alkyne molecule to yield the corresponding ionic fragment of diiron—halogenobenzene [mode ( b )]. Unlike the organoiron complexes which eject neutral molecules, the corresponding free ligands tend to lose mainly radical species. The preparation and properties of nine hitherto unreported styrene—bis(tricarbonyliron) complexes are described.

Trieneiron tricarbonyl and bisallyldi-iron hexacarbonyl π-complexes from photolysis of divinylcyclopropanes induced by iron pentacarbonyl

The photolysis of trans-1-isopropenyl-4-methylenespiro[2.x]alkanes (1)(x= 4,5, or 6) in presence of Fe(CO)5 at room temperature leads to formation (60%) of isomeric mononuclear irontricarbonyl π-complexes of linear trienes [(2) and (3)] and (10%) of a di-ironhexacarbonyl–bis-π-allyl complex of a branched triene (4).

Photoreactions of a methylene-spirane and dispirane with Fe(CO)5. σ,π-Complex formation from a double cyclopropane rearrangement

The major product from the photoreaction of 4-methylenedispiro[2,1,2,3]decane (5) with Fe(CO)5 is shown to be a tricarbonyliron σ,π-complex of structure (7), whereas the products from 4-methylenespiro[2,4]heptane (9) and 4-methylenespiro[2,5]octane (15) are the respective bi-cyclic enones (12)–(13) and (16).

Iron chelators of the pyridoxal 2-pyridyl hydrazone class. Part 4. pKa Values of the chelators and their relevance to biological properties

The proton binding constants (pKa) and species distribution over pH range 1.5–12.0 of two types of biologically active iron chelators (a) pyridoxal type (Lx)—pyridoxal 2-pyridyl hydrazone (PPH) and pyridoxal isonicotinoyl hydrazone (PIH); (b) pyridoxal-betaine type (Ly)—1-[N-methylpyridoxylidenium]-2-[2′-pyridyl] hydrazine iodide (M PH) and 1-[N-ethoxy-carbonylmethylpyridoxylidenium]-2-[2′-pyridyl] hydrazine bromide (EPH) have been determined by glass electrode potentiometry. The lowest pK value in type (a), in the range 2.62 (PPH)–2.45 (PIH) was assigned to pyridinium protonation; the following ionization constants, pKa2= 4.63 (PPH)–4.54 (PIH), to pyridoxylidenium protonation; pKa3= 7.96 (PPH)–7.44 (PIH), to phenolate protonation, and pKa4= 9.96 (PIH)-9.84 (PPH) to amine-hydrazone protonation. At pH 11, in the fully deprotonated forms (Lx2+, and Ly–). At pH ca. 5.0, the pyridoxal-betaines, MPH and EPH, exist predominantly as zwitterions, whereas PPH and PIH are present at that pH predominantly in the neutral, non-zwitterionic, H2Lx form. At higher pH (7.2), PPH and PIH, are present as mixtures of the neutral and the negatively charged monodeprotonated forms (IV).

Trapping of Kekulé structures via co-ordination to iron. Positional isomerism in bis-tricarbonyliron complexes of 3,α-dimethylstyrene

meta-Substituted α-methylstyrene and pentacarbonyliron afford on irradiation two isomeric bis-tricarbonyliron complexes, in each of which one of the Kekule structures is trapped.