Chemoenzymatic Synthesis of a Multivalent Aminoglycoside

A polymeric aminoglycoside was prepared by a facile chemoenzymatic reaction. Boc‐protected aminoglycoside, amikacin, was chemoselectively esterified with divinyl sebacate at a hydroxyl group in the C6″ position by protease from Bacillus subtilis. The resulting 3,6′,3″,4?‐tetra‐N‐Boc‐6″‐O‐vinyl sebacate was copolymerized with maltitol 6‐vinyl sebacate to yield a polymeric amikacin. The polymeric amikacin showed a modest inhibitory effect on in vitro protein synthesis, and a little antibiotic activity in minimum inhibitory concentration (MIC) assay in the presence of protease.

The synthesis of Boc‐protected amikacin ester by an enzyme‐catalyzed (protease) esterification.     

Formation and structure of titanium alkyl phosphates

Titanium alkyl phosphates (TiAP) synthesized by the reactions of Ti(SO(4))(2) with monohexyl, monooctyl, and monodecyl phosphates in aqueous media were characterized by various means. The XRD patterns of TiAP showed a strong diffraction peak and two weak ones below 2theta=15 degrees. The TiAP particle prepared using octyl phosphate gave rise to the lattice patterns having uniform alternating spacings of ca. 0.7 and ca. 2.0 nm. When treated at 900 degrees C, TiAP crystallized as TiP(2)O(7). The chemical formula could be shown as (ROPO(3))(2)Ti.0.44H(2)O. These facts suggest that the TiAP is composed of a multilayer alternating bimolecular layer of alkyl phosphates and hydrated titanium phosphate phase. Alkyl groups in the layers were removed by outgassing above 300 degrees C to give the materials having mesopores with a diameter of ca. 2 nm.     

Applications of the model potential method to transition metal compounds

Model potential parameters and basis sets, presented previously for the transition metal atoms Sc through Hg, are tested in calculations of the transition metal compounds (CuF, CuCl, Cu₂, TiCl₄, ZrCl₄, CoF₆^3?, CoF₆^2?, AgH, AuH, CrF₆, ScO, ZrO, Cr₂, Mo₂). Calculated values of the bond distances, vibrational frequencies, and some transition energies (for Cu₂ and CoF₆^2?) are compared with those given by all-electron calculations with basis sets of high quality. Singlet-triplet splittings in Cu₂ and correlation energies in CrF₆^n? (n = 0, 1, and 2) are also examined. The satisfactory results obtained by these calculations strongly support the contention that the model potential method is a reliable and economical alternative to the ab initio Hartree-Fock-Roothaan method.     

Polymorphisms of 4,5-Bis(4-Methoxyphenyl)-2-(3-Nitrophenyl)-1H-Imidazole as Studied by Solid State NMR

Abstract

Solid state NMR measurements are carried out for polymorphs and inclusion complexes of 4,5-bis(4-methoxyphenyl)-2-(3-nitrophenyl)-1H-imidazole. Observed ¹³C and ¹⁵N chemical shifts are characteristic of each polymorph A, B, C and D. In addition, ¹⁵N chemical shift was a good index for understanding hydrogen bond. VT measurements revealed that B transforms to C between 93 and 113°C. From PSTMAS and ¹H solid echo measurements for AcOET inclusion complex, host molecules have almost same structure as B and guest molecules have the highest mobility of all inclusion complexes.     

Specific and chemoselective multi-alpha-arylation reaction of benzoylformic acid with or without decarbonylation in P(2)O(5)-MsOH and related acidic media

In P(2)O(5)-MsOH, or related acidic media, benzoylformic acid (1) undergoes three types of di- or mono-alpha-arylation reactions with or without decarbonylation ((1) decarbonylative alpha, alpha-diarylation, yielding triarylmethanols 6, (2) decarbonylative alpha-monoarylation, giving benzophenone derivatives 7, and (3) alpha,alpha-diarylation without decarbonylation, affording diarylated carboxylic acids 5) and one simple decarbonylation, without arylation, to form benzoic acid (8), instead of the conventional Friedel-Crafts acylation type reaction. The product ratios are governed by the capability of the acidic medium to form mixed anhydrides with carboxylic acids and the ability of the arenes to accept electrophiles.     

Synthesis of enzymatically crosslinkable peptide-poly(L-lysine) conjugate and creation of bio-inspired hybrid fibers

Poly(L-lysine)s having an Nepsilon-substituted tetrapeptide, Lys-Gly-Tyr-Gly, were synthesized by the coupling of the protected tetrapeptide active ester, Boc-Lys(Z)-Gly-Tyr(Bzl)-Gly (4-hydroxyphenyl)dimethylsulfonium methylsulfate and Nepsilon-group of the poly(L-lysine) side chain. The Nepsilon-substituted tetrapeptide functions as the substrate of tyrosinase and is responsible for the enzyme-mediated interpolymer cross-linking. The degree of Nepsilon-substitution (DS) was mostly controlled by changing the stoichiometry between the Nepsilon-amino groups of the parent poly(L-lysine) and the protected tetrapeptide active ester. Two kinds of samples having DS values of 8.6 and 18 mol-% were prepared. The resulting cationic Nepsilon-(Lys-Gly-Tyr-Gly)-poly(L-lysine) (abbreviated as PLL(GYGK)) was spun into hybrid fibers with the anionic polysaccharide gellan via a polyionic complexation reaction at the interface between aqueous solutions of the two polymers. The mechanical strengths of the PLL(GYGK)-gellan hybrid fibers were superior to those of the original poly(L-lysine)-gellan fibers. The mechanical strength of the hybrid fibers further increased upon the tyrosinase-mediated cross-linking reaction of the PLL(GYGK). This result indicates that the covalent cross-bridge formation between the Nepsilon-substituted peptides significantly contributed to reinforcement of the hybrid fibers. The present study affords a new methodology for reinforcement inspired by a biological process.     

Synthesis of nitrogen-containing heterocycles. 3. Formation and structure of new 1,2,4-triazole derivatives

Treatment of N(3)-[(2-cyano-2-ethoxycarbonyl)vinyl]amino-N(4),N(4)-dimethylaminomethylenehydrazones of aromatic carbonyl compounds with hot acetic acid resulted in the formation of symmetrical gem-bis-(3-dimethylamino-1,2,4-triazol-1-yl)methanes, (3-dimethylamino-1,2,4-triazol-1-yl)arylmethyl acetates, and (3-dimethylamino-1,2,4-triazol-1-yl)alkenes of a gem-diaryl type depending upon whether the carbonyl compound was aldehyde or ketone.     

Revisiting the Bromination of CH Bonds with Molecular Bromine by Using a Photo‐Microflow System

The photobromination of C?H bonds by using molecular bromine was reinvestigated under microfluidic conditions. The continuous‐flow method suppressed the production of dibrominated compounds and effectively produced the desired monobrominated products with high selectivity. Rapid bromination of benzylic substrates containing a photoaffinity azide group was achieved without any decomposition.     

Pseudorotaxane-type fluorescent receptor exhibiting unique response to saccharides

Pseudorotaxane formed by reacting beta-cyclodextrin bearing a phenylboronic acid residue with 1-heptyl-4-(4'-dimethylaminostyryl)pyridinium functioned as a novel fluorescent saccharide receptor having unique responses.     

Terphenyl ligand stabilized lead(II) derivatives: steric effects and lead-lead bonding in diplumbenes

The reaction of PbBr(2) with the lithium reagents LiC(6)H(3)-2,6-(C(6)H(3)-2,6-Pr(i)(2))(2) (LiArPr(i)(2)) and Et(2)O.LiC(6)H(3)-2,6-(2,6-Pr(i)-4-Bu(t)C(6)H(2))(2) (Et(2)O.LiArPr(i)(2)Bu(t)) furnished the bromide bridged organolead(II) halides [Pb(mu-Br)ArPr(i)(2)](2) (1) and[Pb(mu-Br)ArPr(i)(2)Bu(t)](2) (2) as orange crystals. Treatment of 1 with a stoichiometric amount of methylmagnesium bromide resulted in the "diplumbene" Pr(i)(2)Ar(Me)PbPb(Me)ArPr(i)(2) (3). The addition of 1 equiv of 4-tert-butylphenylmagnesium bromide to 1 afforded the feebly associated, Pb-Pb bonded species [Pb(C(6)H(4)-4-Bu(t))ArPr(i)(2)](2) (4), whereas the corresponding reaction of tert-butylmagnesium chloride and 1 afforded the monomer Pb(Bu(t))ArPr(i)(2) (5). The reaction of the more crowded aryl lead(II) bromide [Pb(mu-Br)ArPr(i)(3)](2) (Ar = C(6)H(3)-2,6(C(6)H(2)-2,4,6-Pr(i)(3))(2)) with 4-isopropyl-benzylmagnesium bromide or LiSi(SiMe(3))(3) yielded the monomers 6, [Pb(CH(2)C(6)H(4)-4-Pr(i))ArPr(i)(3)], or 7, [Pb(Si(SiMe(3))(3))ArPr(i)(3)]. All compounds were characterized with use of X-ray crystallography, (1)H, (13)C, and (207)Pb NMR (3-7), and UV-vis spectroscopy. The dimeric Pb-Pb bonded (Pb-Pb = 3.1601(6) A) structure of 3 may be contrasted with the previously reported monomeric structure of Pb(Me)ArPr(i)(3), which differs from 3 only in that it has para Pr(i) substituents on the flanking aryl rings. The presence of these groups is sufficient to prevent the weak Pb-Pb bonding seen in 3. The dimer 4 displays a Pb-Pb distance of 3.947(1) A, which indicates a very weak lead-lead interaction, and it is possible that this close approach could be caused by packing effects. The monomeric structures of 6 and 7 are attributable to steric effects and, in particular, to the large size of ArPr(i)(3).