A novel and widespread class of ketosynthase is responsible for the head-to-head condensation of two acyl moieties in bacterial pyrone biosynthesis

• Darko Kresovic,
• Florence Schempp,
• Zakaria Cheikh-Ali and
• Helge B. Bode

Beilstein J. Org. Chem. 2015, 11, 1412–1417, doi:10.3762/bjoc.11.152

• , 60438 Frankfurt am Main, Germany 10.3762/bjoc.11.152 Abstract The biosynthesis of photopyrones, novel quorum sensing signals in Photorhabdus, has been studied by heterologous expression of the photopyrone synthase PpyS catalyzing the head-to-head condensation of two acyl moieties. The biochemical

• photopyrone synthase (PpyS), which catalyzes the head-to-head condensation of two acyl moieties. Ketosynthases (KS) are the key enzymes involved in the biosynthesis of fatty acids and polyketides [8]. They are known to catalyze C–C bond formations via a Claisen condensation between acyl- and malonylthioesters

• OleA, which is part of the olefin biosynthesis in Xanthomonas campestris by promoting a head-to-head condensation of two long-chain fatty acid thioesters to form a long-chain β-ketoacid that can be further processed to an olefin [14]. KS with acylating activity have been reported in the cervimycin [15

Synthesis and characterization of the cyanobenzene-ethylenedithio-TTF donor

• Sandrina Oliveira,
• Dulce Belo,
• Isabel C. Santos,
• Sandra Rabaça and
• Manuel Almeida

Beilstein J. Org. Chem. 2015, 11, 951–956, doi:10.3762/bjoc.11.106

• crystal structure is made by piling up molecules head to head forming stacks along the b axis (Figure 2) with short S–H contacts (S1–H1B; S4–H2B) in the range 2.751–2.824 Å. Neighbouring stacks are arranged head to tail in the a,c plane with several short contacts between molecules in neighbouring stacks

TTFs nonsymmetrically fused with alkylthiophenic moieties

• Rafaela A. L. Silva,
• Bruno J. C. Vieira,
• Marta M. Andrade,
• Isabel C. Santos,
• Sandra Rabaça,
• Dulce Belo and
• Manuel Almeida

Beilstein J. Org. Chem. 2015, 11, 628–637, doi:10.3762/bjoc.11.71

• methyl group which prevent a shorter distance between molecular planes. Within the stacks the donor molecules are head-to-head (Figure 8). The interactions between stacks are made in two distinct ways along the molecules long axis: 1) In one side the donor molecules interact, with each other, through the

Synthesis and chemosensing properties of cinnoline-containing poly(arylene ethynylene)s

• Natalia A. Danilkina,
• Petr S. Vlasov,
• Semen M. Vodianik,
• Andrey A. Kruchinin,
• Yuri G. Vlasov and
• Irina A. Balova

Beilstein J. Org. Chem. 2015, 11, 373–384, doi:10.3762/bjoc.11.43

• of cinnoline units in both oligomer chains is not regular. Thus there are three types of hydroquinone spacers between head-to-head (red), tail-to-tail (blue) and head-to-tail (orange–purple) oriented cinnoline units in the irregular PAEs chains (Figure 5). Moreover for the hydroquinone moiety that

Biantennary oligoglycines and glyco-oligoglycines self-associating in aqueous medium

• Svetlana V. Tsygankova,
• Alexander A. Chinarev,
• Alexander B. Tuzikov,
• Nikolai Severin,
• Alexey A. Kalachev,
• Juergen P. Rabe,
• Alexandra S. Gambaryan and
• Nicolai V. Bovin

Beilstein J. Org. Chem. 2014, 10, 1372–1382, doi:10.3762/bjoc.10.140

• ]. Results and Discussion Synthesis of biantennary oligoglycines and their glyco derivatives The synthesized biantennary oligoglycines and their glyco derivatives are presented in Figure 1. Analogously to tri- and tetraantennary molecules, oligoglycine antennas are connected according to the ‘head-to-head

Topochemical control of the photodimerization of aromatic compounds by γ-cyclodextrin thioethers in aqueous solution

• Hai Ming Wang and
• Gerhard Wenz

Beilstein J. Org. Chem. 2013, 9, 1858–1866, doi:10.3762/bjoc.9.217

• -to-head dimer. The degree of complexation of coumarin could be increased by employing the salting out effect. Keywords: acenaphthylene; anthracene; coumarin; cyclodextrins; photodimerization; quantum yield; stereoselectivity; Introduction Photochemical reactions have been considered highly

• distribution of products strongly depend both on the solvent [38] and the concentration of COU [39]. In principle, four stereoisomeric dimers are conceivable: syn Head-to-Head (syn-HH), anti-HH, syn-Head-to-Tail (syn-HT), and anti-HH, shown in Figure 5. The photodimerization is very slow in nonpolar media, Φ

• configuration of the dimeric inclusion complex of the guest. Anti-parallel orientation of acenaphthylene within the CD cavity led to the exclusive formation of the anti photo-dimer in quantitative yield. Parallel orientation of coumarin within the complex of a CD thioether led to the formation of the syn head

Self-assembly of 2,3-dihydroxycholestane steroids into supramolecular organogels as a soft template for the in-situ generation of silicate nanomaterials

• Valeria C. Edelsztein,
• Andrea S. Mac Cormack,
• Matías Ciarlantini and
• Pablo H. Di Chenna

Beilstein J. Org. Chem. 2013, 9, 1826–1836, doi:10.3762/bjoc.9.213

• this peak appears at d = 29.4 Å, and the generally less sharp peaks indicate a less ordered self-assembly (Figure 5b). As shown in Figure 6, the scattering peak at d = 35 Å of the n-hexane gel perfectly correlates with the distance of two molecules of 1 arranged head-to-head with completely elongated

• amphiphilic property causes molecules to aggregate into structures that avoid the unfavorable head-to-tail contact, and so, head-to-head and tail-to-tail contacts are directing the self-assembly. In more polar solvents such as DCM, the side chain of the steroid is not fully elongated to avoid the interaction

• conformational study of a single molecule of LMOG 1 (semiempirical, AM1) showed a distance of 18.0 Å for the molecule with the elongated side chain (Figure 6) suggesting a repetitive unit involving a head-to-head self-assembly between two molecules, as explained above. Next, we minimized different modes of head

Inclusion of the insecticide fenitrothion in dimethylated-β-cyclodextrin: unusual guest disorder in the solid state and efficient retardation of the hydrolysis rate of the complexed guest in alkaline solution

• Dyanne L. Cruickshank,
• Natalia M. Rougier,
• Raquel V. Vico,
• Susan A. Bourne,
• Elba I. Buján,
• Mino R. Caira and
• Rita H. de Rossi

Beilstein J. Org. Chem. 2013, 9, 106–117, doi:10.3762/bjoc.9.14

• ]. A crystalline inclusion complex (TRIMEA)2·1 was isolated and shown by X-ray analysis to contain a novel capsule formed by head-to-head contact of the secondary rims of two TRIMEA molecules [5]. The encapsulated fenitrothion molecule showed minor disorder in the form of two rotamers (with respect to

The chemistry of bisallenes

• Henning Hopf and
• Georgios Markopoulos

Beilstein J. Org. Chem. 2012, 8, 1936–1998, doi:10.3762/bjoc.8.225

Synthesis of cross-conjugated trienes by rhodium-catalyzed dimerization of monosubstituted allenes

• Tomoya Miura,
• Tsuneaki Biyajima,
• Takeharu Toyoshima and
• Masahiro Murakami

Beilstein J. Org. Chem. 2011, 7, 578–581, doi:10.3762/bjoc.7.67

• , entries 7 and 8). We propose that the dimerization reaction proceeds through the pathway outlined in Scheme 2. Initially, two molecules of 1a coordinate to a rhodium(I) center at the terminal carbon–carbon double bonds from their sterically less-hindered sides. Oxidative cyclization occurs in a head-to

• -head manner to form the five-membered rhodacyclic intermediate A [22][23][24][25], which is in equilibrium with another rhodacyclic intermediate B via σ–π–σ isomerization. Then, β-hydride elimination takes place with B to form rhodium hydride C stereoselectively. Finally, reductive elimination from C

Supramolecular FRET photocyclodimerization of anthracenecarboxylate with naphthalene-capped γ-cyclodextrin

• Qian Wang,
• Cheng Yang,
• Gaku Fukuhara,
• Tadashi Mori,
• Yu Liu and
• Yoshihisa Inoue

Beilstein J. Org. Chem. 2011, 7, 290–297, doi:10.3762/bjoc.7.38

• modified γ-CDs produced more head-to-head (HH) dimers in much better enantiomeric excesses (ee) for anti-HH dimer compared to native γ-CD. Interestingly, FRET excitation further enhanced the chemical and optical yields of anti-HH dimer up to 36% and 35% ee, for which the highly efficient FRET sensitization

• photochirogenic system for the elucidation of the factors and mechanism that control supramolecular photochirogenesis [12][13][14][15][16][17][18][19][20][21][22]. Photocyclodimerization of AC leads to the formation of four stereoisomeric cyclodimers 1–4, of which syn-head-to-tail (HT) 2 and anti-head-to-head (HH

Stereoselectivity of supported alkene metathesis catalysts: a goal and a tool to characterize active sites

• Christophe Copéret

Beilstein J. Org. Chem. 2011, 7, 13–21, doi:10.3762/bjoc.7.3

• formation of two alkylidene intermediates, M=CHR1 and M=CHR2, and for each intermediate, the alkene can approach in four possible ways: syn/head-to-head, syn/head-to-tail, anti/head-to-head and anti/head-to-tail (Scheme 2). Of these eight possible pathways, four are productive leading to the (Z)- or the (E

Molecular recognition of organic ammonium ions in solution using synthetic receptors

• Andreas Späth and
• Burkhard König

Beilstein J. Org. Chem. 2010, 6, No. 32, doi:10.3762/bjoc.6.32

1-(4-Alkyloxybenzyl)-3-methyl-1H-imidazol-3-ium organic backbone: A versatile smectogenic moiety

• William Dobbs,
• Laurent Douce and
• Benoît Heinrich

Beilstein J. Org. Chem. 2009, 5, No. 62, doi:10.3762/bjoc.5.62

• mesogens impose a bilayer (N = 2) type of organisation on these sublayers, consisting of two head-to-head facing ionic monolayers. The resulting variations of S versus temperature T within the analogous series of various anions but constant chain length (see Figure 7) consist of steep increases