Reductive decomplexation of pi-allyltricarbonyliron lactone complexes using sodium naphthalenide as a route to stereodefined 1,7-diols and 2,3-diene-1,7-diols

Treatment of pi-allyltricarbonyliron lactone complexes, that contain an adjacent leaving group, with lithium naphthalenide causes decomplexation to acyclic dienols in excellent yield and without any stereochemical scrambling of the allylic centre. When an endo complex is employed (E,E)-geometry prevails with good selectivity whereas (Z,E)-geometry dominates in the case of exo complexes. A mechanism consistent with the observed stereo- and regiochemistry is proposed.     

Fully automated multi-step solution phase synthesis using polymer supported reagents: preparation of histone deacetylase inhibitors

The first fully automated multi-step polymer assisted solution phase (PASP) synthesis is described. An array of histone deacetylase (HDAc) inhibitors was prepared by an unattended 4-5 step sequence incorporating in-line 'catch and release' purification.     

Microwave assisted Leimgruber-Batcho reaction for the preparation of indoles, azaindoles and pyrroylquinolines

The development of enhanced conditions for Lewis acid catalysed Leimgruber-Batcho indole synthesis using microwave acceleration is described. This approach has permitted the preparation of a variety of heteroaromatic enamine intermediates in good yield and high purities. Subsequent catalytic hydrogenation reactions, under various conditions including the use of a solid-phase encapsulated catalyst, furnish the corresponding indole derivatives in good yields.     

Non-metal-catalysed intramolecular alkyne cyclotrimerization reactions promoted by focussed microwave heating in batch and flow modes

A number of oligomeric alkynes underwent [2 + 2 + 2] intramolecular trimerization to afford arenes under metal-free conditions using focussed microwave heating.     

Stibatriptycene

Stibatriptycene (1c) has been synthesized by cyclization of 9-(o-chlorophenyl)-9,10-dihydro-9-stibaanthracene (2c) with an excess of lithium piperidide. The general applicability of this ring closure reaction, first developed for the synthesis of phosphatriptycene (1a) and presumed to proceed by nucleophilic attack of a carbanionic centre on a (slowly generated) benzyne, has further been demonstrated by a new synthesis of the known arsatriptycene (1b) and by the synthesis of stibatriptycene (1c). The structure of 1c was confirmed by IR, ¹H NMR and, in particular, by ¹³C NMR spectroscopy.     

A rapid stereocontrolled synthesis of the 3a-hydroxy-pyrrolo[2,3-b]indole skeleton, a building block for 10b-hydroxy-pyrazino[1',2':1,5]pyrrolo[2,3-b]indole-1,4-diones

A two-step selenocyclisation-oxidative deselenaton sequence was used to establish the 3a-hydroxy-pyrrolo[2,3-b]indole core; these tricycles were used as effective precursors to 10b-hydroxy-pyrazino[1',2':1,5]pyrrolo[2,3-b]indole-1,4-diones.     

POSTREPLICATION REPAIR IN AN EXCISION-DEFECTIVE MUTANT OF ESCHERICHIA COLI: ULTRAVIOLET LIGHT-INDUCED INCORPORATION OF BROMODEOXYURIDINE INTO PARENTAL DNA*

Abstract— Ultraviolet (UV) light-induced incorporation of bromodeoxyuridine (BrdUrd) into parental DNA of an excision-defective mutant of Escherichia coli has been observed by selective photolysis of bromouracil (BrUra)-containing regions in the parental DNA. It appears that the BrUra-containing regions occur only in that DNA which has served as a template for normal semiconservative replication. After an exposure at 254 nm which results in one pyrimidine dimer per 45times 10⁶ daltons, incubation in BrdUrd resulted in BrUra–containing regions ˜ 1.5 times 10⁴ nucleotides in length at intervals of ˜ 55 times 10⁶ daltons in the parental DNA. Thus approximately one BrUra-containing region has occurred for every 1.2 pyrimidine dimers in the parental DNA. The observed incorporation of BrdUrd is interpreted in terms of a proposed model for postreplication repair in which genetic exchanges produce single-strand gaps in the parental DNA.     

PHOTOSENSITIZING EFFECTS OF 8-METHOXYPSORALEN ON THE SKIN OF HAIRLESS MICE—11. TRAIN AND SPECTRAL DIFFERENCES FOR TUMORIGENESIS

Abstract. –The absorption and fluorescence characteristics of subchloroplast particles highly enriched in P700 (1 P700 to 10–15 chlorophyll a molecules) and of two artificial systems are presented here. The fluorescence characteristics measured were excitation and emission spectra, and the degree of polarization of fluorescence. The model systems studied were chlorophyll a and pheophytin a in a polystyrene matrix, and a colloidal mixture of these two pigments with bovine serum albumin. Effects of 0.5% sodium dodecyl sulfate on the optical properties of the P700-enriched particles are also described. The importance of pigment-pigment and pigment-protein interactions in determining the fluorescence properties of these particles are discussed. The possible role of pheophytin in these preparations needs further investigation.