Modulating the activity of short arginine-tryptophan containing antibacterial peptides with N-terminal metallocenoyl groups

• H. Bauke Albada,
• Alina-Iulia Chiriac,
• Michaela Wenzel,
• Maya Penkova,
• Julia E. Bandow,
• Hans-Georg Sahl and
• Nils Metzler-Nolte

Beilstein J. Org. Chem. 2012, 8, 1753–1764, doi:10.3762/bjoc.8.200

• with different N- and C-terminal substituents, which showed low micromolar antibacterial activity against various strains of Gram-positive bacteria and moderate activity against Gram-negative bacteria. Interestingly, head-to-tail cyclized RW-based synAMPs with clustered functionalities increased the

Synthesis of trifunctional cyclo-β-tripeptide templates

• Frank Stein,
• Tahir Mehmood,
• Tilman Plass,
• Javid H. Zaidi and
• Ulf Diederichsen

Beilstein J. Org. Chem. 2012, 8, 1576–1583, doi:10.3762/bjoc.8.180

• -to-tail cyclization based on a Boc protocol using the oxidation-labile aryl hydrazide linker [24] and cleavage from the resin under simultaneous cyclization [11]. This method was adapted for the synthesis of the cyclic β-tripeptide 4 (Figure 2). The synthesis of the cyclic β-tripeptide was performed

• -phase chemistry [8][9]. Purification by chromatography is required after each coupling step, and the final cyclization reaction often results in poor yields. Herein, an alternative approach is described based on SPPS followed by on-resin cyclization. Recently, Waldmann et al. discovered an on-resin head

Intramolecular carbenoid ylide forming reactions of 2-diazo-3-keto-4-phthalimidocarboxylic esters derived from methionine and cysteine

• Marc Enßle,
• Stefan Buck,
• Roland Werz and
• Gerhard Maas

Beilstein J. Org. Chem. 2012, 8, 433–440, doi:10.3762/bjoc.8.49

• rearrangement. The short-lived carbonyl ylides derived from methionine and S-benzylcysteine formed head-to-tail dimers by a [3 + 3]-cycloaddition and could be trapped with external dipolarophiles, while the S-allyl derivative 14c yielded the pentacyclic compound 17 by an intramolecular [3 + 2]-cycloaddition

• calculations [24], its energetic contribution in the case of sulfonium ylides stabilised by acceptor substituents is likely to be small. The oxazapolycycles 13a and b are head-to-tail dimers of carbonyl ylides, resulting from a [3 + 3]-cycloaddition. Their constitution and relative stereochemistry was assigned

Liquid-crystalline nanoparticles: Hybrid design and mesophase structures

• Gareth L. Nealon,
• Romain Greget,
• Cristina Dominguez,
• Zsuzsanna T. Nagy,
• Daniel Guillon,
• Jean-Louis Gallani and
• Bertrand Donnio

Beilstein J. Org. Chem. 2012, 8, 349–370, doi:10.3762/bjoc.8.39

• , with a local smectic A2 order for the head-to-tail regions, and local smectic Ad order for the equators (Figure 7). In a departure from cyanobiphenyl based ligands, smectic and columnar structures were observed in a large and systematic study for systems involving swallow-tailed rodlike mesogenic

Natural product biosyntheses in cyanobacteria: A treasure trove of unique enzymes

• Jan-Christoph Kehr,
• Douglas Gatte Picchi and
• Elke Dittmann

Beilstein J. Org. Chem. 2011, 7, 1622–1635, doi:10.3762/bjoc.7.191

• through imino bond formation between the N-terminal and C-terminal amino acids. The responsible enzyme NcpB contains a C-terminal reductase domain that has been shown to catalyze the reductive release of the peptide from the synthetase as an aldehyde followed by spontaneous formation of the imino head-to

• -tail linkage [56]. Cryptophycin Cryptophycins were shown to be produced by terrestrial strains of Nostoc that are either free living or associated with a lichen symbiont. Cryptophycin 1 (15) is the most potent tubulin-destabilizing compound ever discovered and serves as a leading product for the

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

• 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

Symmetry breaking and structure of a mixture of nematic liquid crystals and anisotropic nanoparticles

• Marjan Krasna,
• Matej Cvetko and
• Milan Ambrožič

Beilstein J. Org. Chem. 2010, 6, No. 74, doi:10.3762/bjoc.6.74

• . The directions ± of this unit vector field are physically equivalent, reflecting the so called head-to tail invariance of LC phase on the mesoscopic scale. If ensembles are suddenly quenched from the isotropic to the lower symmetry nematic phase, then unavoidably a domain pattern forms [7]. The reason

Self-association of an indole based guanidinium-carboxylate-zwitterion: formation of stable dimers in solution and the solid state

• Carolin Rether,
• Wilhelm Sicking,
• Roland Boese and
• Carsten Schmuck

Beilstein J. Org. Chem. 2010, 6, No. 3, doi:10.3762/bjoc.6.3

• confirmed the formation of head-to-tail dimers, which are held together by the formation of two salt bridges assisted by a network of six hydrogen bonds (Figure 6). The hydrogen bond distances between the aromatic N...O (2.703 Å), the guanidinium N...O (2.942 Å) and the indole N...O (2.935 Å) are all rather

Competition between local disordering and global ordering fields in nematic liquid crystals

• Matej Cvetko,
• Milan Ambrožič and
• Samo Kralj

Beilstein J. Org. Chem. 2010, 6, No. 2, doi:10.3762/bjoc.6.2

• homogeneous external (e.g., electric or magnetic) ordering field B = BeB, which tends to reorient the director field along eB. Systems with the head-to-tail invariance, where ±Sα orientations are equivalent, are taken into account. This property is characteristic for most LC molecules (where several

• the system using the Lebwohl–Lasher type semi-microscopic description. The orientational order is described in terms of the uniaxial director field exhibiting head-to-tail invariance. We calculate configurations of director fields by minimizing F at temperature zero. Therefore, our results are

Crystal engineering of analogous and homologous organic compounds: hydrogen bonding patterns in trimethoprim hydrogen phthalate and trimethoprim hydrogen adipate

• Packianathan Thomas Muthiah,
• Savarimuthu Francis,
• Urszula Rychlewska and
• Beata Warżajtis

Beilstein J. Org. Chem. 2006, 2, No. 8, doi:10.1186/1860-5397-2-8

• 2, two TMP cations and two hydrogen adipate anions are arranged about an inversion center so that the complementary DDAA (D = donor, A = acceptor) arrays of quadruple hydrogen-bonding patterns are formed. The head-to-tail arrangement of the hydrogen adipate ions leads to a hydrogen-bonded

• neighbouring hydrogen adipate ion(motif VII). This head-to-tail arrangement (carboxyl-carboxylate interaction) of the hydrogen adipate ions leads to hydrogen-bonded supramolecular chain. This is shown in Figure 7. The internal angles at N1 (C2-N1-C6) in the protonated pyrimidine ring of the compounds 1 and 2