TY  - JOUR
AB  - The GE81112 series, consisting of three naturally occurring tetrapeptides and synthetic derivatives, is evaluated as a potential lead structure for the development of a new antibacterial drug. Although the first total synthesis of GE81112A reported by our group provided sufficient amounts of material for an initial in depth biological profiling of the compound, improvements of the routes toward the key building blocks were needed for further upscaling and structure-activity relationship studies. The major challenges identified were poor stereoselectivity in the synthesis of the C-terminal β-hydroxy histidine intermediate and a concise access to all four isomers of the 3-hydroxy pipecolic acid. Herein, we report a second-generation synthesis of GE81112A, which is also applicable to access further representatives of this series. Based on Lajoie's ortho-ester-protected serine aldehydes as key building blocks, the described route provides both a satisfactory improvement in stereoselectivity of the β-hydroxy histidine intermediate synthesis and a stereoselective approach toward both orthogonally protected cis and trans-3-hydroxy pipecolic acid.
AU  - Fayad, S.
AU  - Jafari, A.
AU  - Schuler, S.M.M.*
AU  - Kurz, M.*
AU  - Plettenburg, O.
AU  - Hammann, P.E.*
AU  - Bauer, A.*
AU  - Jürjens, G.
AU  - Pöverlein, C.*
C1  - 67627
C2  - 53934
CY  - 1155 16th St, Nw, Washington, Dc 20036 Usa
SP  - 5597-5608
TI  - Total synthesis of GE81112A: An orthoester-based approach.
JO  - J. Org. Chem.
VL  - 88
IS  - 9
PB  - Amer Chemical Soc
PY  - 2023
SN  - 0022-3263
ER  - 

TY  - JOUR
AB  - Genome sequencing and bioinformatic analysis have identified numerous cryptic gene clusters that have the potential to produce novel natural products. Within this work, we identified a cryptic type II PKS gene cluster (skt) from Streptomyces sp. Tu 6314. Facilitated by linear plus linear homologous recombination-mediated recombineering (LLHR), we directly cloned the skt gene cluster using the Streptomyces site-specific integration vector pSET152. Direct cloning allowed for rapid heterologous expression in Streptomyces coelicolor, leading to the identification and structural characterization of six polyketides (three known compounds and new streptoketides), four of which exhibit anti-HIV activities. Our study shows that the pSET152 vector can be directly used for LLHR, expanding the Rec/ET direct cloning toolbox and providing the possibility for rapid heterologous expression of gene clusters from Streptomyces.
AU  - Qian, Z.*
AU  - Bruhn, T.*
AU  - D'Agostino, P.M.*
AU  - Herrmann, A.
AU  - Haslbeck, M.*
AU  - Antal, N.*
AU  - Fiedler, H.P.*
AU  - Brack-Werner, R.
AU  - Gulder, T.A.M.*
C1  - 57674
C2  - 47851
CY  - 1155 16th St, Nw, Washington, Dc 20036 Usa
SP  - 664-673
TI  - Discovery of the streptoketides by direct cloning and rapid heterologous expression of a cryptic PKS II gene cluster from streptomyces sp. Tü 6314.
JO  - J. Org. Chem.
VL  - 85
IS  - 2
PB  - Amer Chemical Soc
PY  - 2020
SN  - 0022-3263
ER  - 

TY  - JOUR
AB  - A palladium(II)-catalyzed norbornene-mediated regioselective alkylation at the C-2 indole position of N-tert-butyloxycarbonyl (Boc)-protected (S)-tryptophan ethyl ester is reported. The protocol employs mild reaction conditions and is tolerant of a range of functional groups. The reaction proceeds without racemization at the stereogenic center of the amino acid.
AU  - Potukuchi, H.K.
AU  - Bach, T.*
C1  - 28794
C2  - 30859
SP  - 12263-12267
TI  - Selective C-2 alkylation of tryptophan by a Pd(II)/norbornene-promoted C-H activation reaction.
JO  - J. Org. Chem.
VL  - 78
IS  - 23
PB  - Amer. Chemical Soc.
PY  - 2013
SN  - 0022-3263
ER  - 

TY  - JOUR
AB  - The geometries, energies, and electronic properties of possible configurations of Meisenheimer-Wheland (M-W) complexes of sym-triaminobenzenes and 4,6-dinitrobenzofuroxan (DNBF) were investigated theoretically by MP2 and a variety of DFT methods. The pi-pi complex is preferred thermodynamically by more than 15 kcal/mol over the sigma-complexes for the unsubstituted species. However, the N-substituents of the 1,3,5-triaminobenzenes influence the relative stabilities of the alternative configurations significantly. The sigma-syn configuration of the M-W complex of 1,3,5-tris(N-piperidyl)benzene and DNBF has the lowest energy, followed closely by the sigma-anti and pi-pi forms. The small energy differences between different configurations are consistent with the dynamic interconversion of three homomeric structures observed experimentally by NMR. The ca. 1.63 A C-C interring bond exchanges among three equivalent sites. Quantum theory of atoms in molecules (QTAIM) analysis provided insights into the nature of the intermonomer interactions. Charge transfer and sigma bonding account for the stability and remarkably large binding energies of the M-W complexes.
AU  - Jin, P.*
AU  - Li, F.Y.*
AU  - Riley, K.*
AU  - Lenoir, D.
AU  - von Rague Schleyer, P.*
AU  - Chen, Z.F.*
C1  - 919
C2  - 27290
SP  - 3761-3765
TI  - What is the preferred structure of the Meisenheimer-Wheland complex between sym-triaminobenzene and 4,6-dinitrobenzofuroxan?
JO  - J. Org. Chem.
VL  - 75
IS  - 11
PB  - American Chemical Society
PY  - 2010
SN  - 0022-3263
ER  - 

TY  - JOUR
AB  - Generation and NMR studies of novel carbocations and carboxonium ions are reported from sterically hindered stilbene 1,1'-bi(benzocyclobutenylidene) 1, its dimethoxy derivative 5, and from their skeletally rearranged derivatives, namely, the spirocyclic ketone 6, diastereomeric alcohols 7 and isomeric diols 8. Quenching experiments on the carbocations under various conditions resulted in the formation/isolation of several novel covalent adducts. Acid-catalyzed isomerization of the diols 8 produced a remarkable dimeric molecule, whose structure was confirmed by X-ray analysis. Reactions of hindered stilbenes 1 and 5 with Br 2/CDCl 3 were examined via NMR experiments. The experimentally observed carbocations were also studied computationally by GIAO-DFT and by NICS.
AU  - Laali, K.K.*
AU  - Okazaki, T.*
AU  - Bunge, S.D.*
AU  - Lenoir, D.
C1  - 4771
C2  - 25650
SP  - 4092-4100
TI  - Stable ion and electrophilic chemistry of the sterically crowded stilbene 1,1'-Bi(benzocyclobutenylidene) and its derivatives.
JO  - J. Org. Chem.
VL  - 73
IS  - 11
PB  - American Chemical Society
PY  - 2008
SN  - 0022-3263
ER  - 

TY  - JOUR
AU  - Chiappe, C.*
AU  - de Rubertis, A.*
AU  - Lemmen, P.*
AU  - Lenoir, D.
C1  - 21279
C2  - 19391
SP  - 1273-1279
TI  - Steric Strain and Reactivity: Electrophilic Bromination of trans-(1-Methyl-2-adamantylidene)-1- methyladamantane.
JO  - J. Org. Chem.
VL  - 65
PY  - 2000
SN  - 0022-3263
ER  - 

TY  - JOUR
AU  - Turner, W.V.
AU  - Gäb, S.
C1  - 40557
C2  - 12554
SP  - 1610-1613
TI  - Preparation of 1-chloroalkyl hydroperoxides by the addition of hydrogen chloride to carbonyl oxides.
JO  - J. Org. Chem.
VL  - 57
IS  - 5
PY  - 1992
SN  - 0022-3263
ER  - 

TY  - JOUR
AU  - Gano, J.E.
AU  - Park, B.-S.
AU  - Subramaniam, G.
AU  - Lenoir, D.
AU  - Gleiter, R.
C1  - 19611
C2  - 12720
SP  - 4806-4808
TI  - Unusual, Cofacial Structure of a Sterically Congested Stilbene: (Z)-2,2,5,5-Tetramethyl-3,4-diphenyl-3-hexene.
JO  - J. Org. Chem.
VL  - 56
PY  - 1991
SN  - 0022-3263
ER  - 

TY  - JOUR
AB  - On the basis of its spectroscopic and chemical properties, an unstable intermediate previously detected in the ozonolysis of trans-2,3-dichloro-2-butene (1) in inert solvents is reformulated as 1,1-dichloroethyl hydroperoxide (5). Ozonolysis of 1 in ethyl formate saturated with anhydrous HCl leads to high yields of this intermediate. 1,1-Dichloroethyl peroxide ion (10), rather than 5, is believed to be the precursor of acetyl 1,1-dichloroethyl peroxide (8), which is produced in higher yield on ozonolysis of 1 in the presence of tetraalkylammonium chloride.
AU  - Gäb, S.
AU  - Turner, W.V.
C1  - 42738
C2  - 38249
SP  - 2711-2714
TI  - 1,1-Dichloroethyl hydroperoxide and 1,1-dichloroethyl peroxide ion as intermediates in the ozonolysis of 2,3-dichloro-2-butene.
JO  - J. Org. Chem.
VL  - 49
IS  - 15
PY  - 1984
SN  - 0022-3263
ER  - 

TY  - JOUR
AB  - Chlorine-photosensitized oxidation of several perchlorinated olefins as neat liquids or adsorbed on silica gel leads to stable perchlorinated peroxides with α-chlorine atoms; these were identified by spectroscopic and X-ray crystallographic methods.
AU  - Gäb, S.
AU  - Turner, W.V.
AU  - Korte, F.
AU  - Born, L.*
C1  - 34187
C2  - 38629
SP  - 173-175
TI  - Stable peroxides from chlorine-photosensitized oxidation of perchlorinated olefins.
JO  - J. Org. Chem.
VL  - 47
IS  - 1
PY  - 1982
SN  - 0022-3263
ER  -