Peter Bentley

Fluorescence and light fastness of aminoanthraquinones

Abstract The fluorescence emission spectra and quantum yields of thirteen 1-amino-2-amino- and 1,4-diamino-anthraquinones in a variety of solvents have been determined. The quantum yield values for the 1-amino derivatives are decreased on N-alkylation and also by the N-substitution of acyl or aryl groups. Both emission wavelength maxima and quantum yields of the 2-substituted derivatives are markedly sensitive to solvent polarity. These observations are discussed in relation to the light fastness of the aminoanthraquinones on polyester fabric.

Transformations using benzyl 6-isocyanopenicillanate

The preparation and C-6 epimerisation of benzyl 6α-isocyanopenicillanate is described. By utilising the activating influence of the isocyanide group and a subsequent conversion of this group into an amino-group under mild conditions, 6α-substituted penicillins were thereby prepared. Additionally, several novel rearrangements of these isocyanides are described.

Synthesis and biological activity of some fused β-lactam peptidoglycan analogues

The derivatives (12), (14), (15), (19), and (22), in which a mono- or di-peptide unit is linked to 6-aminopenicillanic acid, have been prepared according to normal synthetic peptide procedures. The structures of the side chains were chosen by analogy with the D-isoglutamyl-L-lysyl sequence present in the cell-wall peptidoglycan of Staphylococcus species. The antibacterial activities of the derivatives were measured and the results are discussed.

Total synthesis of β-lactamase inhibitors based on the 4-oxa-1-azabicyclo[3.2.0]heptan-7-one ring system

4-(2-Bromoethoxy)azetidin-2-one (4), 4-(1,3-dibromoisopropoxy)azetidin-2-one (5), 4-(1-benzyloxy-3-chloroisopropoxy)azetidin-2-one (6), 4-[(1-bromomethyl)prop-2-enoxy]azetidin-2-one (7), and 4-[3-bromo-1(bromomethyl)propoxy]azetidin-2-one (8) have been synthesised and their use for the preparation of bicyclic β-lactam compounds has been investigated. On treatment with base, (4) gave 4-oxa-1-azabicyclo[3.2.0]heptan-7-one, (5) gave (3RS, 5SR)-3-(bromomethyl)-4-oxa-1-azabicyclo[3.2.0]heptan-7-one (9) and its (3RS, 5RS)isomer (21), and (6) gave (3RS, 5SR)-3-(benzyloxymethyl)-4-oxa-1-azabicyclo[3.2.0]heptan-7-one (10) and its (3RS, 5RS)-isomer (22). Compound (7) did not undergo cyclisation; instead elimination occurred to give a conjugated diene, 4-(1-methylene-prop-2-enoxy)azetidin-2-one. Cyclisation of (8) gave not only the fivemebered-ring compound but also the six-membered-ring compound, 4-(bromomethyl)-5-oxa-1-azabicyclo[4.2.0]octan-8-one.Compounds (9) and (21) reacted with a variety of nucleophilic reagents to give products derived by displacement of bromide. Catalytic hydrogenation of (10) removed the benzyl group to give the hydroxymethyl compound. Removal of the benzyl group from (22) under these conditions gave a hydroxymethyl compound which rearranged on silica gel to give 3,9-dioxa-7-azabicyclo[4.2.1]nonan-4-one.Differences in the 1H n.m.r, spectra of pairs of stereoisomers such as (9) and (21), and (10) and (22), are discussed. Relative stereochemistries have been deduced for two natural products previously isolated from Streptomyces clavuligerus. Compound (9) and some of its relatives have been found to be β-lactamase inhibitors.

The light fastness and flash photolysis of benzanthrone disperse dyes on poly(ethylene terephthalate)

Abstract The I.S.O. light fastness grade of 15 benzanthrone disperse dyes on poly(ethylene terephthalate) (PET) fabric has been determined and the flash photolysis behaviour of benzanthrone dyes in PET film has been examined. The dyes of poor light fastness all show transient absorption on flash photolysis and the transients observed on flashing films dyed with benzanthrone and its 3-methoxy-, 6-hydroxy- and 6-amino-derivatives are identified as the triplet states of the dyes. 6-Anilino- and 8-hydroxy- benzanthrone, on the other hand, have good light fastness and films dyed with these derivatives show no transient absorption on flash photolysis. The higher light fastness of PET dyed with 6-anilino- and 8-hydroxybenzanthrone is attributed to the low triplet yields of these dyes.

The photochemistry of benz[de]anthracen-7-ones. Part I. Electronic absorption and emission spectroscopy

The electronic absorption and emission spectra of benz[de]anthracen-7-one and some of its 3-, 4-, 6-, and 8-substituted derivatives have been investigated. The lowest excited singlet states of the benzanthracenone derivatives are all π–π* in nature. 8-Aminobenz[de]anthracen-7-one has a broad, structureless, longest wavelength absorption band which disappears on protonation of the ground state. In contrast, the 6-amino-derivative possesses marked vibrational structure in its absorption spectrum and is much more resistant to protonation of the ground state

The photochemistry of benz[de]anthracen-7-ones. Part III. Fluorescence quantum yield and continuous photolysis studies

Fluorescence quantum yields are reported on benzanthrone and a range of its 3-, 4-, 6-, and 8-substituted derivatives in solvents of differing polarity. With benzanthrone and the 3-methoxy-derivative the quantum yields obtained in alcoholic solutions are in general higher than those in other solvents and this effect is discussed in the light of estimated potential energy levels and configurations of the lowest excited states. The continuous photolysis results are in accord with the configuration assignments and with earlier flash photolysis results on the same compounds.

The photochemistry of benz[de]anthracen-7-ones. Part II. Flash photolysis

The primary photochemical processes following light absorption by benz[de]anthracen-7-one and some of its 3-, 4-, 6-, and 8-substituted derivatives have been studied by laser ns and conventional µs flash photolysis. The transients observed on laser flash photolysis of benz[de]anthracen-7-one and its 4-anilino-, 6-hydroxy-, and 6-amino-derivatives in benzene are the lowest triplet excited states. The rate constants for triplet quenching by oxygen have been determined. The 6-hydroxy- and 6-amino-benz[de]anthracen-7-ones behave rather like benz[de]anthracen-7-one itself whereas the 8-hydroxy- and 8-amino-derivatives show no transient absorption or dye fading on µs flash photolysis and show only weak transient absorption on laser photolysis. These observations are discussed in relation to the overall light stability of the benz[de]anthracen-7-ones.