A. Taylor

Chemical transformations on the surface of [60]fullerene: Synthesis of [60]fullereno[1′,2′:4,5]oxazolidin-2-one

Abstract Base-induced α-elimination from substituted O -4-nitrophenylsulfonylhydroxamic acids has been used as a mild source of nitrenes for capture by [60]fullerene; rearrangment of the resulting [60]fullereno[1′,2′:2,3]aziridine bearing a N -ethoxycarbonyl grouping under the influence of phenol/chlorotrimethylsilane results in the quantitative formation of the title compound which can be cleaved to yield 1-hydroxy-2- N -methylamino[60]fullerene.

Aziridino[2′,3′ : 1,2][60]fullerene

Thermal elimination of isobutene and CO2 from N-tert-butoxycarbonylaziridino[2′,3′ : 1,2][60]fullerene 4 provides a clean and efficient route to aziridino[2′,3′ : 1,2][60]fullerene 1, an isolable and stable solid.

Studies leading to the large scale synthesis of polyesters using enzymes

The ability of immobilised Candida antarctica lipase to catalyse the condensation of diols and diacids was studied. The range of acids investigated (in condensations with butane-1,4-diol) included adipic, maleic, fumaric, itaconic, (E)-hex-3-enedioic and acetylenedicarboxylic acids, while the diols studied, in condensations with adipic acid, encompassed ethane-, propane-, butane-, pentane- and hexane-diols as well as (Z)-but-2-ene-1,4-diol and but-2-yne-1,4-diol. The oligomerization of hexane-1,6-diol and adipic acid was most facile and was chosen for scale-up. A mechanism for the polycondensation process is proposed.

Birch reduction of C60—a new appraisal

Contrary to a previous report that Birch reduction of C60 affords C60H36 as the principal product, laser desorption-laser photoionisation time-of-flight (L2TOF), laser desorption Fourier transform ion cyclotron resonance (FTICR), and liquid secondary ion mass spectrometry (LSIMS) show collectively that a mixture of polyhydrofullerenes, containing C60H18 through to C60H36 with a skewed distribution centred on C60H32 is formed, the discrepancy in results arising from the thermal lability of this mixture of polyhydrofullerenes when subjected to the elevated temperatures (>250 °C) required for mass spectroscopic studies using direct-insertion heated probes.

Aziridino[2′,3′ : 1,6][60]fullerene: isolation of the first closed [5,6]-bridged fullerene adduct

In addition to the expected formation of closed [6,6]-bridged azmdinofullerene 3 by reaction of [60]fullerene with singlet oxycarbonylnitrenes, small amounts (ca. 10%) of previously undetected closed [5,6]-adducts 5 have been isolated, and are thought to arise by trapping of triplet nitrenes.

Isonitrile acids from cultures of the fungus Trichoderma hamatum(Bon.) Bain. aggr., X-ray structure

Two acids have been isolated from cultures of the above fungus as the corresponding methyl esters; one is shown by X-ray crystallographic analysis to be methyl 3-(3-isocyano-6-oxabicyclo[3.1.0]hex-2-en-5-yl) acrylate (1), the other is probably methyl 3-(3-isocyanocyclopent-2-enylidine) propionate (2).

Unprecedented ring expansion of [60]fullerene: incorporation of nitrogen at an open 6,6-ring juncture by regiospecific reduction of oxycarbonylaziridino-[2′,3′:1,2][60]fullerenes. Synthesis of 1a-aza-1(6a)-homo[60]fullerene, C60H2NH

Upon treatment with zinc in glacial acetic acid, N-oxycarbonylaziridino[2′,3′: 1,2][60]fullerenes 3 undergo a reversible reductive cleavage of the bridgehead C–C bond to provide the first examples of birdged fulleroids 4 having an open 6,6-ring juncture; deprotection of the N-tert-butoxycarbonyl derivative 4a allows the convenient synthesis of C60H2NH 5, the parent member of this new class of bridged fulleroids.

Sporidesmins. Part XIII. Ovine III-thrift in Nova Scotia. Part III. The characterisation of chetomin a toxic metabolite of Chaetomium cochliodes and Chaetomium globosum

Chetomin, one of the antibiotic metabolites of Chaetomium cochliodes and C. globosum has been isolated as an amorphous, glass-like solid. Elemental analysis of chetomin, its diacetate, and its bistrimethylsilyl ether, mass spectroscopy of its tetrathiomethyl derivative, and n.m.r. spectroscopy indicate the molecular formula to be C31H30N6O6S4. The formation of a tetra-S-methyl derivative and a bismonosulphide indicated the presence of two epidithiodioxopiperazine ring systems like those present in chaetocin, a metabolite of C. minutum, a conclusion supported by the close similarity of the c.d. of the two metabolites. The u.v. spectrum of chetomin was the same as that of echinulin. These facts, and an interpretation of the n.m.r. spectra of chetomin and its derivatives, lead us to believe that the molecule contains an indole, an indoline, and two epidithiodioxopiperazine systems. A biogenetically plausible assembly of these structural features is shown [formula (XIII)], but other formulae are possible.

THE STEREOCHEMISTRY OF POLYSULPHIDES

Abstract : A few natural products having asymmetric polysulphide moieties have been isolated, and improved methods of synthesis have enabled other asymmetric polysulphides to be secured. The availability of these compounds has enabled n.m.r. studies to be made, and these investigations have shown that the chemical shift of atomic nuclei adjacent to a sulphur group depends on its asymmetry. In addition, these compounds exhibit different circular dichroism. These advances have led to an increase in our knowledge of the stereochemistry of sulphur compounds and it therefore seems appropriate to present a review of the subject at this time. The review is divided into four sections dealing with sulphur, acyclic polysulphides, organic cyclic polysulphides, and inorganic cyclic polysulphides. (Author)

Isolation, synthesis and reactivity of a key macrobislactone; 1,4,7-trioxacyclotridecane-8-13-dione

Abstract Macrobislactone 1, 1,4,7-trioxa-cyclotridecane-8-13-dione, believed to be the cause of the fogging of car windscreens by an oily film, has been formally synthesised from diethylene glycol and adipic acid and its content in commercial polyester formulations has been estimated. Study of its ring-opening potential towards both anionic and enzymatic reagents reveal surprizing stability in polyester formulations, coupled with anomalous high susceptibility in the pure state to the lipase Candida antarctica, immobilized as Novozyme™. Assay of macrobislactone 1 in a range of polyesters suggest that there is significantly more of this key lactone present than trends would predict Reasons for this behaviour are advanced following modelling studies and from thermodynamic considerations.