Preparation of Some Benzyl D-Glucuronatesfrom 4-Methoxybenzylidene Derivatives of D-Glucuronic Acid

 Because of the low stability of the benzyl ester linkage in benzyl 1,2:3,5-di-O-benzylidene-α-D-glucofuranuronate during the removal of the benzylidene groups by acid hydrolysis and/or hydrogenolysis, 4-methoxybenzylidene groups were used to block the free hydroxyl groups of D-glucuronic acid. Several benzyl esters of D-glucuronic acid were prepared, and their relative rates of acid catalyzed hydrolysis were determined by liquid-chromatographic separation of the reaction mixture and subsequent diode array detection.     

Stereospecific Synthesis of D-Glycero-D-ido-oct-2-ulose

Summary.  D-Glycero-D-gulo-heptose reacted with 2,2-dimethoxypropane to give its 2,3:6,7-di-O-isopropylidene derivative. Its base-catalyzed addition to formaldehyde resulted in the formation of 2,3:6,7-di-O-isopropylidene-2-C-(hydroxymethyl)-D-glycero-D-gulo-heptofuranose. After acid hydrolysis of this aldolization product, a new branched-chain aldose, 2-C-(hydroxymethyl)-D-glycero-D-gulo-heptose, was obtained, which was stereospecifically rearranged under the catalytic action of molybdic acid to D-glycero-D-ido-oct-2-ulose. Received October 17, 2000. Accepted December 4, 2000     

Synthesis of Urine Drug Metabolites: Glucuronosyl Esters of Carboxymefloquine,Indoprofen, (S)‐Naproxen,and Desmethyl (S)‐Naproxen

Abstract

A general procedure for the synthesis of 1‐O‐acyl‐β‐D‐glucuronic acids using the benzyl 1-O-trichloroacetimidoyl-2,3,4-tri-O-benzyl-D-glucopyranuronate 6 as donor is exemplified by the synthesis of the urine metabolites of (S)‐naproxen, desmethyl (S)‐naproxen, indoprofen, and carboxymefloquine. The key intermediate benzyl 2,3,4‐tri‐O‐benzyl‐D‐glucopyranuronate 5 is easily accessible in four steps (29%) from the peracetylated β-D-glucuronic acid 1.     

Microbial and Enzymatic Synthesis of Optically Pure D- and L-3-Trimethylsilyl-alanine by Deracemization of D,L-5-Trimethylsilyl-methyl-hydantion

Summary.  The sterospecificities of hydantoinases and N-carbamoyl amino acid amidohydrolases (N-carbamoylases) from different microbial sources were investigated for the stereoselective syntheses of the unnatural silicon-containing amino acids D- and L-3-trimethylsilyl-alanine (3) from the respective racemic hydantoin D,L-1. In a preparative biotransformation, whole resting cells of Agrobacterium sp. IP I 671, immobilized in a Ca-alginate matrix, were used for the synthesis of amino acid D-3 in 88% yield and 95% enantiomeric excess. Since the purified D-N-carbamoylase from Agrobacterium sp. IP I 671 was shown to be 100%D-selective, the enantiomeric purity of 95% of D-3 arising from the transformation with the immobilized cells must be explained by the participation of a further, L-selective N-carbamoylase or, which is more likely, by racemization of the final hydrolysis product by the action of an amino acid racemase. Isolated hydantoinases from Bacillus thermoglucosidasius, Thermus sp., Arthrobacter aurescens DSM 3745, and Arthrobacter crystallopoietes DSM 20117 turned out to be stereospecific for the conversion of the D-form of hydantoin D,L-1. The enantiomerically pure L-form of 3 was also prepared. It was synthesized from racemic N-carbamoyl amino acid D,L-2 by enantiomer-specific hydrolysis of the L-form in presence of L-N-carbamoylase from Arthrobacter aurescens DSM 3747. Received December 20, 1999. Accepted January 7, 2000     

Beauveria bassiana ATCC 7159 Containsan L-Specific a-Amino Acid Benzamidase

Summary.  Biotransformation of a series of racemic N-benzoyl α-amino acids by the fungus Beauveria bassiana ATCC 7159 results in isolation of the corresponding D-amino acid benzamides in high enantiomeric purity and yield. Received December 20, 1999. Accepted January 21, 2000     

A Selective Conversion of Benzylic Alcohols to the Corresponding Carbonyl Compounds by Means of an Ag(III) Complex

Summary.  Carbonyl compounds of the type XPhCOR (R = H, Me, Ph; X = H, Me, Cl, Br) are prepared in high yields by reaction of the corresponding benzylic alcohols XPhCHOHR with KNa₄ [Ag(HIO₆)₂]×12H₂O in alkaline solution. This method allows the selective oxidation of benzylic alcohols in compounds containing other types of alcoholic functional groups. Received January 18, 2000. Accepted (revised) February 23, 2000     

Phase Gratings in Photoreactive Polymers:A Way to Optically Pumped Organic Lasers

Summary.  Poly-(4-vinylbenzyl-thiocyanate) (PVBT) was investigated as a photoreactive polymer which changes its refractive index upon UV irradiation as is required for the production of phase gratings. After UV irradiation, the refractive index of PVBT films increased from n_D ²⁰ = 1.629 to n_D ²⁰ = 1.660 (Δn = +0.031). The change in the refractive index resulted mainly from the photoinduced isomerization of thiocyanate (SCN) to isothiocyanate (NCS) groups. It was possible to modify irradiated PVBT with 1-naphthylmethyl amine which lead to a further increase of the refractive index. Both the isomerization and the modification were followed with FTIR spectroscopy. This modification of the irradiated zones also yields an advantageous stabilization of phase gratings enscribed in PVBT. The investigations were carried out in the realm of novel organic distributed feedback (DFB) lasers. Received August 22, 2000. Accepted September 22, 2000     

Kinetic Studies on the Complexation of Chromium(III) with some Amino Acids in Aqueous Acidic Medium

Summary.  The kinetics of the formation of the 1:3 complex of chromium(III) with L-glutamic acid and DL-lysine were studied spectrophotometrically at and 550 nm. The reaction was found to be first order in both reactants. Increasing the hydrogen ion concentration from 3.2×10⁻⁵ to 1.0×10⁻³ molċdm⁻³ retarded the reaction rate which is of the form . Values of 28.8 and 63.6 kJċmol⁻¹ were obtained for the energy of activation and −184 and −116 Jċ K⁻¹ċmol⁻¹ for the entropy of activation for L-glutamic acid and DL-lysine. The logarithms of the formation constants of the two complexes were found to be 5.9 and 5.1. Received January 7, 2000. Accepted (revised) March 8, 2000     

Environmentally Friendly Arylmethylation of Aromatics with Benzyl Halides Using Envirocat EPZ10® as the Catalyst

Summary.  The Friedel-Crafts arylmethylation of aromatics with benzyl halides or bis-(bromomethyl)-benzene in the presence of Envirocat EPZ10? affords selectively para-arylmethylated products in good yields. Isolation of pure products involving an eco-friendly procedure and recyclability of the catalyst are important features of this method. Received January 17, 2000. Accepted (revised) March 2, 2000     

peri-naphthylenediamines

o-Nitro ando,o′-dinitro derivatives of 1,8-bis(dimethylamino)naphthalene and its acenaphthene analog were prepared for the first time by direct nitration with nitrogen dioxide or tetranitromethane. When 5,6-bis(dimethylamino)acenaphthene was treated with nitric acid in AcOH or MeCN or with nitronium tetrafluoroborate in MeCN, nitration was accompanied by partial demethylation of one of the NMe₂ groups. For Part 27, see Ref. 1. Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1215–1220, July, 2000.     

Novel Carboxyl Esterase Preparations for the Resolution of Linalyl Acetate

Summary.  Biocatalytic resolution of the tertiary terpene alcohol (±)-linalool was accomplished via hydrolysis of its corresponding acetate ester using two highly enantiospecific enzymes (E > 100). The latter were identified in a crude cell-free extract of Rhodococcus ruber DSM 43338 and could be separated by (partial) protein purification. Since they showed opposite enantiopreference, they were termed (R)- and (S)-linalyl acetate hydrolase (LAH). The activity and selectivity of the enzyme preparations was markedly dependent on the fermentation conditions. Received November 18, 1999. Accepted January 21, 2000     

Synthesis and properties of poly(amide–imide)s containing a N-methylcarbazole group

A new dicarboxylic acid monomer containing the N-methylcarbazole and imide structures, 3,6-bis(trimellitimido)-N-methylcarbazole (I), was prepared from the condensation of 3,6-diamino-N-methylcarbazole (c) and trimellitic anhydride. The diamine c was synthesized in three steps starting from the methylation of carbazole, followed by nitration and catalytic hydrazine reduction. A series of N-methylcarbazole-containing poly(amide–imide)s were synthesized by direct polycondensation from the diimide–diacid I with various aromatic diamines. These poly(amide–imide)s had inherent viscosities of 0.66–1.47 dl/g and were readily soluble in a variety of organic solvents, including N-methyl-2-pyrrolidone and N,N-dimethylacetamide (DMAc). Transparent, flexible, and tough films of these polymers could be cast from DMAc solutions, and these films exhibited excellent mechanical strength. The glass-transition temperatures of these poly(amide–imide)s were in the range 317–362 °C. All the poly (amide–imide) did not degrade noticeably below 480 °C in nitrogen, and the 10% weight loss temperatures and char yields at 800 °C were above 520 °C and 60% in nitrogen, respectively, indicating high thermal stability. Received: 8 February 2000/Accepted: 23 March 2000     

Effect of the temperature on the composition and ratio of hydrolysis products of 1,2-dichlorotetramethyldisilane

The hydrolysis of 1,2-dichlorotetramethyldisilane was studied at different temperatures. At reduced temperatures, the hydrolysis gave permethylcyclo(oxadisilanes) [(Me₂Si)₂O]_n (n = 2 and 3) and α,ω-dihydroxypermethyloligo(oxadisilanes) HO[(SiMe₂)₂O]_mH (m = 1–5). The formation of the latter was proved by the GC-MS method. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 722–724, April, 2006.     

Synthesis of Cryptococcus neoformans Capsular Polysaccharide Structures. Part V: Construction of Glucuronic Acid‐Containing Thioglycoside Donor Blocks

Abstract

Glucuronic acid‐containing di‐ and trisaccharide thioglycoside building blocks, ethyl (benzyl 2,3,4‐tri‐O‐benzyl‐β‐D‐glucopyranosyluronate)‐(1 → 2)‐3‐O‐allyl‐4,6‐di‐O‐benzyl‐1‐thio‐α‐D‐mannopyranoside, ethyl (benzyl 2,3,4‐tri‐O‐benzyl‐β‐D‐glucopyranosyluronate)‐(1 → 2)‐6‐O‐acetyl‐3‐O‐allyl‐4‐O‐benzyl‐1‐thio‐α‐D‐mannopyranoside and ethyl (2,3,4‐tri‐O‐benzyl‐β‐D‐xylopyranosyl)‐(1 → 4)‐[(benzyl 2,3,4‐tri‐O‐benzyl‐β‐D‐glucopyranosyluronate)‐(1 → 2)]‐3‐O‐allyl‐6‐O‐benzyl‐1‐thio‐α‐D‐mannopyranoside, corresponding to repetitive structures in the capsular polysaccharide (CPS) of Cryptococcus neoformans, have been synthesized. The blocks contain an orthogonal allyl group in the 3‐position of the mannose residue to allow formation of the (1 → 3)‐linked mannan backbone of the CPS and benzyl ethers as persistent protecting groups to facilitate access to acetylated target structures. The glucuronic acid moiety was introduced using an acetylated trichloroacetimidate donor and the xylose residue employing the benzoylated bromo sugar to ensure β‐selectivity in the couplings. Exchange to benzyl protecting groups was then performed at the di‐ or trisaccharide level. Assembly of suitable blocks employing DMTST as promoter in diethyl ether then afforded, in high yield and with stereoselectivity, a protected pentasaccharide corresponding to a C. neoformans serotype D CPS structure.     

Ab initio study of bonding trends for f0 actinide oxyfluoride species

 Fully relativistic, four-component Dirac–Fock calculations and quasirelativistic pseudopotential calculations at different ab initio levels are used to study the bonding trends among the naked, triatomic [OAnO] ^q+ groups or the oxyfluorides [AnO _n F _m ] ^q with f ⁰ configurations. The triatomic f ⁰ series is suggested to range from the bent ThO₂ via the linear OPaO⁺ to at least NpO₂ ³⁺, a possible new gas-phase species. The neutral oxyfluoride molecules include the experimentally unknown NpO₂F₃ and PuO₂F₄. The latter is a candidate for the so far unknown oxidation state Pu(VIII), which is found to lie considerably above Pu(VI), but to be locally stable. Their all-oxygen isoelectronic analogues are NpO₅ ³⁻, known in the solid state, and the unknown PuO₆ ⁴⁻. Further possible candidates for Pu(VIII) are PuO₄(D _4h ) and the cube-shaped PuF₈(O _h ). Isoelectronic UF₈ ²⁻ is calculated to be D _4d , in agreement with experiment. Received: 18 May 2001 / Accepted: 21 June 2001 / Published online: 11 October 2001     

Enzymatic hydrolysis by Humicola lanuginosa lipase of poly(lactic acid)–poly(glycolic acid) monolayers

 The enzymatic hydrolysis by Humicola lanuginosa lipase (HLL) of spread insoluble monolayers of poly (α-hydroxy acid)s with various molecular weights and various lactic–glycolic molar ratios was studied using a barostat surface balance. The interfacial hydrolysis under enzyme action leads to the progressive fragmentation of the polymer molecules. The appearance at the interface of charged insoluble fragments was detected by measuring the surface potential, while the solubilization of the small soluble fragments was detected by measuring the decrease in the surface area. The data obtained were used to test the mode of fragmentation: either random or chain-end scission. The catalytic specific activity of HLL was estimated in the framework of the random scission model and compared with the activities obtained for the hydrolysis of simple molecules of di- and tri-glycerides organized as monolayers or emulsion. Received: 9 August 1999 Accepted: 4 January 2000     

Complexation of Indole-3-acetic Acid with Iron(III): Influence of Coordination on the π-Electronic System of the Ligand

Summary.  The iron(III) complex of indole-3-acetic acid (1) was prepared, and its physicochemical properties, mode of iron(III) coordination, and electronic structure were studied using UV/Vis, diffuse reflectance infrared Fourier transform (DRIFT), and transmission ⁵⁷Fe M?ssbauer spectroscopic techniques. The data obtained provide evidence that iron(III) is not only coordinated by the carboxylic O-donor atom, but also via the conjugated π-electronic system of the pyrrole moiety involving both the non-shared electronic pair of the heteroatom and the C(2)*C(3) double bond. Considering the well-known increased sensitivity of the pyrrole residue in indole derivatives to oxidation as compared to the benzene ring, as well as the formation of a triple complex (peroxidase-1-O₂) proposed for the enzymatic 1 oxidative degradation mechanism involving as a key step the Fe³⁺ → Fe²⁺ transition in the enzyme form as discussed in literature, it is concluded that iron(III) coordination with 1 can influence the redox properties of the pyrrole ring by affecting its π-electronic system. Received September 17, 2000. Accepted (revised) October 31, 2000     

Synthesis of Enantiopure Chiral Perhydrobenzimidazole and Hexahydroquinoxaline Derivatives

Summary.  Starting from 2-anilino-2-ethoxy-3-oxothiobutyric acid anilides and (R, R)-or (S, S)-trans-1,2-diaminocyclohexane, chiral C2-disubstituted perhydrobenzimidazole and trans-4a,5,6,7,8,8a-hexahydroquinoxaline derivatives were obtained depending on the polarity of the solvent. Received April 10, 2000. Accepted May 2, 2000     

Lipase-Catalyzed Resolution of Ibuprofen

Summary.  The resolution of ibuprofen by transesterification of its corresponding vinylester using lipase B from Candida antarctica is described. Compared to transesterification or hydrolysis of the ibuprofen ethyl ester (E < 2, 28–48 h), the reaction with vinylesters occurred significantly faster (1.5–5 h) and with considerably higher enantioselectivity (E = 8–39). Received December 20, 1999. Accepted January 12, 2000