Calozeylanic acid,a new bark acid from three calophyllum species (guttiferae)

Calozeylanic acid has been isolated from the bark of three $\text{calophyllum}$ species: $\text{C.lankaensis}$ (= $\text{C.zeylanicum}$), $\text{C.thwaitesii}$ and $\text{C.walkeri}$. Its structure has been established as 2(R),3(R)-2,3-Dimetyl- 5-hydroxy-6-(3-methylbutanyl)-6-(3,7-dimethylocta-3,6-dienyl)-7-oxo-8- (2-carboxy-1-phenylethyl)-2,3,6,7-tetrahydrobenzo-4-pyrone.     

Total synthesis of slow reacting substances (SRS's): 6-epi-leukotriene C and 6-epi-leukotriene D

6-$\text{Epi}$-leukotrienes C and D (3 and 4) have been synthesized unambiguously via the 5($\text{S}$), 6($\text{R}$)-epoxide (5,6-$\text{cis}$) which is isomeric with leukotriene A. These 6-$\text{epi}$-leukotrienes are less active (especially 4) than leukotrienes C and D (1 and 2) and have not been found in substantial quantity in natural SRS sources.     

Pathways for migration and cleavage of the S-peptide unit of the leukotrienes

Sulfoxides of leukotriene C ($\text{2}$) and various analogs ($\text{5}$, $\text{8}$) undergo a 1,7-migration of sulfur (forming diastereomers $\text{3}$, $\text{6}$, and $\text{9}$, respectively) with noteworthy facility. Generation of the S-halo derivatives of leukotriene C in water results in heterolysis of the CS bond to give (5S, 12R)- and (5S, 12S)-6-$\text{trans}$-leukotriene B in a process which mimics biochemical deactivation.     

Polar substituent effects in the solvolysis of 2-methyl-2-endo-norbonyl 2,4-dinitrophenyl ethers

The solvolysis rates of tertiary 2-endo-norbonyl derivatives $\text{2}$ are less strongly controlled by the polar effects of substituents at C(6) than the rates of the secondary analogues $\text{1}$.     

Nature of the catalytic cycle in iridium-complex catalysed hydrogenation of unsaturated alcohols

The $\text{endo}$ face specific reduction of $\text{endo}$-6-methylenebicyclo[2,2,2]octan-2-ol and $\text{endo}$-6-methy[bicyclo [2,2,2]-oct-5-en-2-ol with D₂ and iridium catalysts is accompanied by deep-seated isotopic redistribution through an intramolecular mechanism, although only two deuterium atoms are incorporated on average. Individual isotopomers of the product may be identified in the ¹³C N.m.r. spectrum at 125 MHz. and their ratio is generally consistent with a mechanism in which product is formed by breakdown of an alkyliridium trihydride. Iridium (and rhodium) catalysts part-isomerise the exocyclic olefin to its endocyclic isomer $\text{via}$ an Ir-allyl intermediate without incorporation of deuterium. The reduction of 3-methylcyclohex-2-enol is likewise accompanied by considerable scrambling, with isotopic enrichment occurring at C2, C3, C4 and C5 of the product, $\text{trans}$-3-methylcyclohexanol. Deuteration occurs exclusively on the hydroxyl-bearing face of the molecule.     

A short and efficient synthesis of 4-hydroxy-5-(1-hydroxyalkyl)-γ-butyrolactones

The cycloaddition of α,β-epoxyaldehydes or ketones ($\text{2}$) with the ketene acetal MeHC=C(OMe)₂ ($\text{1}$) gives epoxyoxetanes ($\text{3}$) in high yields. Without isolation they can be transformed into 4-hydroxy-5-(1-hydroxyalkyl)-γ-butyrolactones ($\text{6}$) via the epoxy esters $\text{4}$ and trihydroxy esters ($\text{5}$). The lactones $\text{6}$ appear to be valuable precursors for the synthesis of 5-(1-hydroxyalkyl)-3-methyl-2-5H-furanones ($\text{7}$) and 3-methyl-5-ylidene-2-5H-furanones ($\text{8}$)     

Metal—metal bonding in dinuclear complexes of platinum(I). The crystal and molecular structure of carbonyl(chloro)-bis-μ-[bis(diphenylphosphino)methane]diplatinum hexafluorophosphate

The structure of [Pt₂Cl(CO) (μ-Ph₂PCH₂PPh₂)₂] [PF₆] was determined by $\text{X}$-ray methods and refined to $\text{R}$ = 0.082, using diffractometric intensities of 5646 independent reflections. The crystals are monoclinic, space group $\text{P}$2₁/$\text{n}$, $\text{a}$ = 12.919(3), $\text{b}$ = 15.576(6), $\text{c}$ = 25.151(5)Å, β = 94.82(3)°, $\text{Z}$ = 4. They are built of octahedral hexafluorophosphate anions and dinuclear platinum(I) cations. The latter contain PtCl and PtCO fragments linked to one another by a PtPt σ-bond and by two bridging bis(diphenylphosphino)methane ligands. The platinum atoms are in square planar environments and the dihedral angle between the two coordination planes is 40.1°. Selected bond lengths are: PtPt 2.620(1), PtCl 2.384(5), PtC 1.89(3) and PtP 2.291(5) – 2.308(5)Å.     

1,6-dithia-spiro[4.4]nonadiene aus 2-thiazolin-5-thionen

4,4-Dimethyl-2-phenyl-2-thiazolin-5-thione ($\text{4}$) reacts with 2,3-diphenylcyclopropenone ($\text{2a}$) at 145°C and with benzonitrilio-2-propanide ($\text{6}$) at room temperature to yield the 1,6-dithia-spiro[4.4]nonadienes $\text{5}$ and $\text{7}$, respectively.     

Solid state reactions to CdTeMoO6 and its structural characterization

CdTeMoO₆ has been obtained by solid state reactions of CdMoO₄ with orth. TeO₂ at 425°C, with tetr. TeO₂ at 470°C, and with H₆TeO₆ at 490°C. Its crystal structure belongs to the tetragonal system (space group $\text{P4}\text{n}$ or $\text{P4}\text{nmm}$ with unit cell dimensions a = 5.279(2) Å, c = 9.056(2) Å. The specificity of this compound in the allylic oxidation reactions should be strictly related to its structural features, among which the presence of cis MoO₂ groups could be very important.     

The effect of environment on the reactions of thiiranium ions

The thiiranium ion formed by the reaction of $\text{Z}$-1-phenylpropene and (4-ClC₆H₄S)₂SC₆H₄ClSbCl₆ in CH₂Cl₉ at ?70°C reacts with Cl^? to form both $\text{erythro}$- and $\text{threo}$-Markownikoff B-chlorosulfides.     

4,6-Thioanhydro-hexopyranosides,synthesis and chemical behaviour of methyl 2-0-p-toluenesulfonyl-4,6-thioanhydro-α-d-gulopyranoside

Methyl 4-0-benzoyl-6-bromo-6-deoxy-α-D-glucopyranoside ($\text{1}$, Figure 1) was converted, via the corresponding ditosylate $\text{2}$, into methyl 2,3-di-0-p-toluenesulfonyl-4-0-benzoyl-6-S-acetyl-6-thio-α-D-glucopyranoside ($\text{3}$) by a selective nucleophilic displacement of 6-bromo-group with thioacetate. Unexpectedly, on treating the compound $\text{3}$ with an excess of sodium methoxide in benzene-methanol (1:1) at room temperature, methyl 2-0-p-toluenesulfonyl-4,6-thioanhydro-α-D-gulopyranoside ($\text{4}$) was obtained in a yield of 84%. In order to determine the structure of the relatively unstable oily product $\text{4}$, some stable crystalline derivatives ($\text{5}$, $\text{6}$ and $\text{7}$) were prepared. Detailed analysis of the ¹H-NMR-spectra (200 MHz) of $\text{6}$ and $\text{7}$ gave the conclusive evidence for the structure of $\text{4}$ A self-imposing mechanism of the clean and smooth transformation of $\text{3}$ to $\text{4}$ is proposed, involving: a) formation of $\text{9}$ (Figure 2) as a crucial intermediate and b) a highly regioselective epoxide opening in $\text{9}$ (at C-4) by an intramolecular nucleophilic attack of the mercaptide anion from C-6.     

An approach to the enantiocontrolled synthesis of pseudomonic acids via a novel mono—claisen rearrangement

A short, efficient approach to a key chiral intermediate for the synthesis of pseudomonic acids A and C is delineated.Pseudomonic acids A($\text{1a}$), B($\text{1b}$), and C($\text{2}$) are members of a novel of “C-glycopyranoside” antimicrobial agents which have recently attracted synthetic attetion.² Presently, we wish to report a short efficient stratedy towards the total synthesis of opticaly active pseudomonic acids. The sequence is highlighted by a novel controlled mono-Claisen rearrangement and a highly regioselective π-allylpalladium mediated displacement.Diacetyl-(L)-arabinal ($\text{3}$)³ was converted to the bis-ketenesilylacetal $\text{4}$ and warmed to 60°C according to the Ireland ester-enolate Claisen rearrangement method.⁴ Over a period of ≈5h, smooth conversion to a major rearranged product $\text{5}$ was observed by 300 MHz NMR. The identity of $\text{5}$ was confirmed by direct desilylation and methylation (KF, KHCO₃, H₂O, HMPA, CH₃I). After flash chromatography, compound $\text{7}$ was isolated in 55% overall yield from $\text{3}$. Careful inspection of the crude methylation product revealed the presence of ≈5% doubly rearranged product $\text{6}$.The rearrangement of $\text{4}$ to $\text{5}$ is a unique example of a selective mono-Claisen rearrangement in which the rate of a second similar Claisen rearrangement ($\text{5}$ → $\text{6}$) is much slower under the reaction conditions. Although the reasons for this interesting selectivity are unclear at this time,⁵ in practice, the mono-Claisen rearrangement obviates the need for selective differentiation of the two hydroxyl groups, a difficult task at best, in this case.Palladium mediated allylic acetate displacement provided an ideal method for introduction of a second chemodifferentiated side chain with allylic retention and retention of stereochemistry. Alkylation of $\text{7}$ with sodiothylmalonate using 5 mole % Pd(O)dppe₂⁶ was unusually facile (<45 min, 25°C, THF). After semi-preparative HPLC, essentially a single regio- and stereoisomer was isolated in 96% yield.⁷ Structure $\text{8}$ was confirmed by extensive ¹H-NMR decoupling, as well as an off-resonance ¹³C-NMR experiment. In particular, H₁ (δ 4.53) was coupled vicinally to H₆ and H₆′ (5 Hz, 8 Hz) and H₂ (1.5 Hz), and allylically to H₃ (2 Hz). In contrast, H₄ (δ 2.78) was coupled to H₇ (10 Hz), H_5e and H_5a (1.8 Hz, 4 Hz), H₃ (5 Hz), and H₂ (<1 Hz). In addition, H₁ and H₄ exhibited a small long range coupling constant (J = <1 Hz). The coupling constants rule out

regioisomer $\text{9}$ and are fully consistent with the indicated conformation, which minimizes 1,3-diaxial-like interactions.Finally, catalytic osmylation of $\text{8}{}^8$ gave a single cis-diol $\text{10}$ in nearly quantitative yield. Appending of suitably functionalized side chains to provide an enantiocontrolled synthesis of pseudomonic acids A($\text{1a}$) and C($\text{2}$) is in progress.^9,10     

Leitfähigkeit dotierter (μ-1,4-diisocyanobenzol)phthalocyanina toeisen(II)-verbindungen

Conductivity of doped (μ-1,4-diisocyanobenzene)phthalocyaninatoiron(II)-compounds. - The (μ-1,4-diisocyanobenzene)phthalocyaninatoiron(II)-compounds $\text{2a}$, $\text{3a}$, $\text{5a}$ and $\text{6a}$ are doped with iodine leading to air stable powders which are stable up to 100°C. They were characterized by elemental analyses, TGA/DTA, IR-, resonance Raman- and ⁵⁷Fe-Mössbauer spectroscopy. Increasing dopant levels result in higher electronic conductivities up to 10^?2 S/cm and in decreasing activation energies.     

Substituent influence on the indolization with pcl3 of some o,m,p-substituted phenylhydrazones

The indolization of deoxybenzoin $\text{o}$,$\text{m}$,$\text{p}$ (Me, MeO, Cl), $\text{p}$-NO₂ and $\text{m}$-EtO-phenylhydrazones (1) by the above reaction has been examined. All the reactions are carried out at room temperature and high yields of the corresponding indoles (2) are obtained even when -NO₂ substituent is present. In this case longer reaction time is necessary. Alkoxyphenylhydrazones give the corresponding indoles (2) in high yields without showing collateral reactions which indeed are present in several Fischer routes on these derivatives. $\text{m}$-Substituted phenylhydrazones (1) give a mixture of 4- and 6-substituted indoles in which the 6-isomer is always prevalent, a feature not inherent in the Fischer reactions. The regioselectivity is enhanced by the substituent steric hindrance increasing. The reaction can be also carried out at 0°C with a further improvement of its regioselectivity.     

Comparative reactions between aziridines and F2, COF2, CF3OF

In CFCl₃, aziridines $\text{I}$ react with F₂(6 %/N₂,  20°C), COF₂ (20 %/N₂,  40°C) and CF₃OF [1] (20 %/N₂,  40°C).Substitution products are obtained : l-(aziridine)carbonyl fluorides $\text{II}$ and l-Fluoroaziridines $\text{III}$

In (Et)₂O, aziridines $\text{I}$ react with COF₂ (20 %/N₂, 10°C) and we have the carbonyl fluorides $\text{IV}$.

Products IV can be thermally decomposed into β fluoro isocyanates.In CFCl₃, N substituted aziridines $\text{V}$ react with F₂(6%/N₂, 20°C) and with CF₃OF [2] (20%/N₂, 40°C). No reaction is observed with COF₂in our conditions (5% to 25%/N₂, 80°C to + 40°C).Addition products are obtained : N Fluoro amines β fluorinated $\text{VI}$, N Fluoro and NN difluoro amines β trifluoro methoxylated $\text{VII}$ and $\text{VIII}$.

with R = SO₂Ø, COØNO₂, Cl.     

Eugenol and safrole as starting materials for the synthesis of 3-alkyl muconic acid mono and dimethyl esters and 4,4-dialkyl butenolides

Compounds $\text{1b-e}$ and $\text{2b-d}$ prepared from eugenol ($\text{1a}$) and safrole ($\text{2a}$) respectively were submitted to ozonation in methanol at 0°C. The 3-alkyl muconic acid dimethyl esters $\text{4b-e}$ were produced from $\text{1b-e}$ (～ 45%), while starting from $\text{2b-d}$ the 3-alkyl muconic acid monomethyl esters $\text{6b-d}$ were obtained regiospecifically (～ 75%). These latter compounds were transformed (～ 85%) into the 4,4-dialkyl butenolides $\text{7b-d}$.     

New tetrahydropyrans from a marine sponge

Two new tetrahydropyrans have been isolated from the sponge Haliclona sp. From chemical and spectroscopic evidence they are shown to be (1′$\text{R}$, 2$\text{S}$, 2″$\text{E}$, 5$\text{R}$, 6$\text{R}$)-2-(1′-bromethyl)-2,5-dimethyl-6-(penta-2″,4″-dienyl)-tetrahydropyran and (1′$\text{R}$, 2$\text{S}$, 5$\text{R}$, 6$\text{R}$)-2-(1′-bromoethyl)-2,5-dimethyl-6-(pent-4″-enyl)-tetrahydropyran.     

Synthesis and crystal structure of a π-allyl iron carbonyl complex derived from a fluorocarbon containing ligand by loss of fluorine

The β-chlorovinylphosphines R₂P$\text{C  CCl(C}$F₂)₃ (R = C₆H₅, C₆H₁₁) react with Fe(CO)₅ yielding compounds of stoichiometry

. The crystal structure of one of these (R = C₆H₁₁) has been determined from X-ray diffraction data and refined by least-squares to $\text{R}$ = 0.037 (2313 reflections with $\text{I}$ > 2.3σ_$\text{I}$). Crystals are triclinic, space group $\text{P}$$\text{1}$, $\text{a}$ = 10.253(5), $\text{b}$ = 15.590(7), $\text{c}$ = 9.390(4)Å, α = 99.88(3), β = 103.21(2), γ = 92.02(2)°, $\text{Z}$ = 2. The fluorinated π-allyl group is σ-bonded to one Fe atom and π-bonded to the other.     

A short and stereoselective synthesis of the (±) Prelog-Djerassi lactonic acid

Reaction of meso-4-carbomethoxy-2-methylpentanal ($\text{1}$) with crotyltri-n-butyltin at ?78°C in the presence of 1 eq BF₃·OEt₂, followed by the lactonization with BF₃·OEt₂, gave 6-(1-methylallyl)-3,4,5,6-tetrahydro-3,5-dimethyl-2-pyranone ($\text{2a}$) with the correct stereochemistry (erythro, anti-Cram) in 92% yield, which was converted to the title compound ($\text{3}$) in 85% yield upon the ozonolytic cleavage of the double bond.