Studies on the formation and incorporation of streptolidine in the biosynthesis of the peptidyl nucleoside antibiotic streptothricin F

Streptothricin F (STF, 1) is a peptidyl nucleoside antibiotic produced by Streptomyces lavendulae. Studies were conducted to address the formation and timing of incorporation of the arginine-derived base streptolidine (4) during the biosynthesis of 1. [guanidino-(13)C]Streptolidine (10) was prepared by modification of an established method and used in whole-cell incorporation experiments. Analysis of the purified STF by (13)C NMR revealed a 1.9% enrichment of the guanidino carbon, confirming 4 as an advanced precursor to 1 and supporting proposals that 1 is assembled via a convergent biosynthetic pathway. To identify advanced intermediates in the conversion of L-arginine to 4, (2S,3R)-[guanidino-(13)C]capreomycidine (32) was prepared from oxazolidine aldehyde (18) via 1,1-dimethylethyl (4R,1'S)-4-(1',3'-diaminopropyl)-2,2-dimethyl-3-oxazolidinecarboxylate (30). Treatment of 30 with Br(13)CN yielded the corresponding diprotected amino alcohol, which was readily converted to 32. The STF isolated from whole-cell incorporation experiments with 32 showed no significant (13)C enrichment at the guanidino carbon. These results suggest that 32 may be an enzyme-bound intermediate, unable to enter the cell, or is not a precursor to STF.     

Synthesis of methyl 3-deoxy-3-methylaminoarabinopyranoside,a component of some aminoglycoside antibiotics

Amino sugar $\text{1}$ has been synthesized in racemic form as a mixture of anomers from sorbic aldehyde. An intramolecular N-sulfinyl dienophile Diels-Alder strategy was used to stereospecifically generate the chiral centers of pentose $\text{1}$.     

Studies on streptothricins VII. Determination of the ninhydrin-positive fragments of streptothricin antibiotics

Summary 1. A method for the quantitative analysis of the hydrolyzates of streptothricin antibiotics has been developed and has been used to determine the composition of representatives of the six types of this group of substances.2. The empirical formulae previously established for the new antibiotics have been confirmed and a proposed structure of the six types of streptothricins is discussed.3. On the basis of the results obtained, the hypothesis put forward that the empirical and structural formula of the antibiotic streptoline proposed by American workers is incorrect. A new empirical formula is proposed for this compound.Khimiya Prirodnykh Soedinenii, Vol. 1, No. 2, pp. 117–122, 1965     

Synthesis of novel ionic polymers containing arsonic acid group

Synthesis of ortho‐ and para‐acryloylaminophenylarsonic acids (o‐AAPHA and p‐AAPHA) monomers and their homopolymers, useful as ion‐exchange materials, are reported. Both the monomers and homopolymers are synthesized with >90% yield. The structures of the new compounds are determined by NMR and FTIR spectroscopy. Molecular weights of the polymers are determined from light scattering measurements and found to be M_w = 38,759 g/mol for o‐AAPHA polymer and M_w = 31,347 g/mol for p‐AAPHA polymer. Good thermal stability of the new compounds derived from their intra‐ or intermolecular hydrogen bondings suggests their applications as proton‐exchange membrane at high temperatures. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1627–1634, 2006     

Photophysical investigations of interpolymer interactions in solutions of a pyrene substituted poly(acrylic acid), poly(vinyl amine), poly(1-aminoacrylic acid), and poly(1-acetylaminoacrylic acid)

Photophysical properties of the pyrene chromophore covalently bound to poly(acrylic acid) were used to investigate the interactions of a pyrene substituted poly(acrylic acid) (1) with poly(vinyl amine hydrochloride) (PVAm), poly(1-aminoacrylic acid) (PDA), and poly(1-acetylaminoacrylic acid) (PADA) in aqueous solutions. A number of photophysical parameters were obtained from fluorescence emission and excitation spectra, the deconvolution of decay curves for pyrene monomer, and excited state complex fluorescence and the quenching of pyrene monomer fluorescence by nitromethane in polymer solutions. These photophysical parameters were considered to reflect the inter- and intrapolymer interactions in solutions of 1 , PVAm, PDA, and PADA. The formation of interpolymer complexes between 1 and PVAm was noticed at low (< 4) as well as high (> 8) values, whereas PDA and 1 formed interpolymer complexes at low pH only. No interpolymer complex formation was detected in solutions of 1 and PADA under low or high pH conditions. The structures of interpolymer complexes formed between 1 and PVAm under low and high pH conditions were found to be determined by the conformation of 1 . There were significant differences in the interpolymer interactions of 1 and PDA in comparison to those of 1 and PVAm; in particular, the fluorescence from the excited state complex was enhanced in solutions of 1 and PVAm but quenched in solutions of 1 and PDA. The investigations of terpolymer solutions of 1 , PVAm, and PADA indicated that the nature of interpolymer complexes formed in terpolymer solutions was determined by Coulombic interactions of the amino and carboxylic group containing polymers.     

Synthesis,structures, and property studies on Zn(II), Ni(II), and Cu(II) complexes with a Schiff base ligand containing thiocarbamide group

A Schiff base ligand containing thiocarbamide group of 4-phenyl-1-(4-methoxyl-1-phenylethylidene)thiosemicarbazide (HL) and its three mononuclear metal complexes of ZnL₂ (1), NiL₂ (2), and CuL₂ (3) have been synthesized. Elemental analysis, IR, and X-ray single crystal diffraction characterizations for the ligand and the three complexes have been carried out. In the three complexes, the central metallic ions of Zn²⁺, Ni²⁺, and Cu²⁺ coordinate with two deprotonated ligands of L⁻, respectively. In 1, Zn²⁺ ion adopts a distorted tetrahedral geometry, while in 2 and 3, both the Ni²⁺ and Cu²⁺ ions possess distorted square planar configurations. For the four compounds, UV–Vis spectra have been measured and DFT calculations at B3LYP/LANL2DZ level of theory prove that the electronic spectra of HL and 1 are corresponding with electronic transitions of n → π* and π → π* in the ligand itself and the electronic spectra of 2 and 3 are attributed to intraligand electronic transitions as well as d–d electronic transitions. Electrochemical investigations reveal that the different metal–ligand interactions have changed the peak shapes and peak locations, which are corresponding with the DFT-B3LYP/LANL2DZ calculational results. Fluorescence spectra measurements indicate that the ligand emits purple fluorescence and the complex 1 emits stronger blue fluorescence, while the complexes 2 and 3 quench fluorescence. The thermal analyses result show that the three complexes undergo two similar decomposition processes because of their similar geometric configurations.     

Synthesis of anacardic acids, 6-[8(Z),11(Z)-pentadecadienyl]salicylic acid and 6-[8(Z),11(Z),14-pentadecatrienyl]salicylic acid

11-Chloro-3-methoxy-2-undecenal was synthesized from 8-bromooctanol, and an annelation reaction with this aldehyde and ethyl acetoacetate proceeded to give the ethyl 6-(8-chlorooctyl)salicylate. Ethyl 6-(8-chlorooctyl)salicylate was converted to ethyl 6-(7-formylheptyl)-2-methoxybenzoate through the iodide after protection of the phenolic hydroxyl group. Finally, the Wittig reaction with the aldehyde and triphenylphosphonium iodides in the presence of BuLi gave the methoxybenzoates, and then treatments of these methoxybenzoates with BBr3 in CH2Cl2 and 10% NaOH in ethanol gave 6-18(Z),11(Z)-pentadecadienyllsalicylic acid (anacardic acid 3) and 6-[8(Z),11(Z),14-pentadecatrienyl]salicylic acid (anacardic acid 4) which were isolated from plants of the anacardiaceae.     

Synthesis and crystal structures of Cd(II), Ni(II), and Mn(II) complexes of 1H-benzotriazole-1-acetic acid

Three new complexes: [Cd(btaa)(bipy)(CH₃COO) · H₂O] _n (1), [Ni(btaa)₂(H₂O)₄ · 6H₂O] _n (2), and [Mn(btaa)₂(H₂O)₂] _n (3) (bipy = 2,2′-bipyridine, Hbtaa = 1H-benzotriazole-1-acetic acid) were prepared and characterized by IR, elemental analyses, thermogravimetric analyses, and single-crystal X-ray analyses. In 1, cadmium ions are linked by btaa ligands into 1-D linear chains; the chains are extended into layers through C–H ··· O hydrogen bonds and π–π stacking interactions. Complex 2 is a mononuclear structure, extended to a 3-D network through multiple intermolecular hydrogen bonds. In 3, manganese is bridged by carboxylate groups of btaa in the syn–skew bidentate mode in two directions to form a 2-D grid-like framework with a (4, 4) topology. The solid-state fluorescence spectrum of 1 shows that the excitation peak is at 355 nm while the maximum emission peak is at 424 nm.