Synthetic Approach Toward Antibiotic Tunicamycins - VII Synthesis of Tunicamine and Tunicaminyl Uracil Derivative

A higher carbon carbohydrate moiety of antibiotic tunica-mycins named tunicamine has been synthesized in a protected form. The key reaction step of the synthesis is a potassium fluoride catalyzed Henry reaction of a 5-nitroribose derivative and a dial do-galactosamine derivative. The tunicamine derivative has been converted to a tunicaminyl uracil derivative by condenation with bis(trimethylsilyl) uracil.     

New methods and reagents in organic synthesis. 50. a stereoselective synthesis of a derivative of L-vancosamine,a carbohydrate component of the antibiotics vancomycin and sporaviridin

A derivative of L-vancosamine, a carbohydrate component of the antibiotics vancomycin and sporaviridin, has been prepared from L-lactic acid in a highly stereoselective manner.     

Divergent cycloaddition and ring-closing metathesis approaches to indolizidine and pyrrolo[1,2-a]azepine skeletons from a chiral precursor: an expeditious route to (-)-8-epi-swainsonine triacetate

[reaction: see text] A divergent strategy for the synthesis of diverse azabicyclic ring systems has been developed in which a chiral N-allylpyrrolidine derivative, obtained from a carbohydrate precursor was converted to (-)-8-epi-swainsonine triacetate by RCM and to a pyrrolo[1,2-a]azepine derivative and a 3-hydroxymethyl-substituted indolizidine by N-allylcarbohydrate nitrone and nitrile oxide cycloadditions.     

A rigid lanthanide binding tag for NMR structural analysis of carbohydrates

The first synthesis of a carbohydrate molecule covalently bound to a rigid lanthanide binding tag is reported. This derivative has been designed as a new tool to provide long-range restraints for structural elucidation and molecular recognition studies of carbohydrates, thus extending the methodology already developed for proteins.     

Reductive Amination of the Lysine N ε-Amino Group Leads to a Bivalent Glyco-Amino Acid Building Block Suited for SPPS

Aiming at the synthesis of structurally altered glycopeptides to probe multivalency effects in carbohydrate recognition, a glyco-amino acid building block was prepared, carrying a bivalent carbohydrate branching unit. This new mannosylated lysine derivative was shown to be fully suitable for solid-phase peptide synthesis.     

Synthetic Approach Toward Antibiotic Tunicamycins, 4. X-Ray Crystal Structure Analysis of a Higher-Carbon Nitro Sugar

Abstract

A higher-carbon carbohydrate, a derivative of undecose has been synthesized by the potassium fluoride-catalyzed addition of a nitro sugar to a sugar aldehyde. The addition of methyl 5-de-oxy-2,3-O-isopropylidene-5-nitro-β-D-ribofuranoside to methyl 2-benzyloxycarbonylamino-2-deoxy-3,4-O-isopropylidene-α-D-galacto-dialdopyranoside-(1, 5) yielded a single diastereomer of the nitro undecose derivative. The absolute configuration of two chiral centers of the derivative has been established by the X-ray crystal structure analysis.     

Supramolecular carbohydrate scaffold-catalyzed synthesis of tetrahydroquinolines

Natural supramolecular carbohydrate scaffold-catalyzed synthesis of tetrahydroquinoline derivatives by the reaction of aromatic amine and cyclic enol ether in excellent yield with high diastereoselectivity has been developed. Carbohydrates, cellulose, and starch were converted into their sulfonic acid derivative and these scaffolds exhibit efficient catalytic properties, along with excellent cost effectivity and recyclability.     

De novo synthesis of aceric acid and an aceric acid building block

The de novo synthesis of an aceric acid thioglycoside building block and the total synthesis of the plant carbohydrate aceric acid are described via a highly convergent strategy. Aldol reaction of acetaldehyde and a protected tartaric acid derivative provided the open chain carbohydrate. Subsequent acid treatment yielded the aceric acid thioglycoside in 35% total yield over five steps. Oxidative cleavage of the thioketal in the open chain carbohydrate and basic hydrolysis of the methyl ester furnished fully deprotected aceric acid in 31% yield over six steps.     

Carbohydrate mimic of 2-deoxystreptamine for the preparation of conformationally constrained aminoglycosides

The synthesis of a carbohydrate mimic of 2-deoxystreptamine (2-DOS) is described starting from d-ribose. Crucial steps of the synthesis involve a stereoselective nitroaldol condensation and deoxygenation via elimination-in situ reduction. Moreover, glycosylation of the carbohydrate 2-DOS derivative with a phenyl thioglycoside donor in the presence of TTBP and AgOTf followed by ring-closing metathesis yielded a conformationally restricted aminoglycoside analogue.     

Preparation of chiral cyclopropanes with a carbohydrate fragment from levoglucosenone

Levoglucosenone (a chiral α,β-unsaturated ketone derivative of cellulose) underwent stereoselective cyclopropanation with sulfonium ylides to form chiral trisubstituted cyclopropanes annulated with the carbohydrate moiety in high yields.     

Regioselective activation of glycosyl acceptors by a diarylborinic acid-derived catalyst

A derivative of diphenylborinic acid promotes catalytic, regioselective Koenigs-Knorr glycosylations of carbohydrate derivatives bearing multiple secondary hydroxyl groups. Robust levels of selectivity for the equatorial OH group of cis-1,2-diol motifs are demonstrated in reactions of seven acceptors derived from galactose, mannose, fucose, and arabinose using a variety of glycosyl halide donors. Catalyst control presents a new means of generating defined glycosidic linkages from unprotected or minimally protected carbohydrate feedstocks.     

Semipreparative High-Pressure Liquid Chromatography of Synthetic Carbohydrates

Abstract

A rapid and effective method has been developed for the purification of hundred-milligram quantities of water-soluble synthetic carbohydrates. The method utilizes a 30 cm x 7.8 mm i.d. column packed with Waters Associates carbohydrate analysis packing in conjunction with isocratic water-acetonitrile elution and refractive index detection. The generality of this method is illustrated by its application to 13 sucrose derivatives and one derivative each of D-fructose and α,α-trehalose.     

Synthesis of 5-O-β-Iodoethyl-D-Glucofuranose

ABSTRACT

The preparation of an iodinated derivative of D-glucose where a β-iodoethyl moiety has been introduced at O-5 is presented. In such an analogue the existence of pyranose forms is precluded and the iodinated tag lies in a region of the carbohydrate not judged essential for recognition by the glucose transport protein; also noteworthy in such a compound is the stability of the carbon-iodine bond, a prerequisite for its potential use in SPECT medical imaging.     

Total synthesis of brasoside and littoralisone

The first total syntheses of littoralisone (1) and brasoside (2) have been achieved in 13 overall steps. Both natural products are forged from a common intermediate which is rapidly assembled using organocatalytic technology, including a proline-catalyzed alpha-aminoxylation and a contra-thermodynamic intramolecular Michael addition. Application of the two-step carbohydrate synthesis technology has enabled to access a selectively substituted glucose derivative for use as an intramolecular cycloaddition tether. This synthesis culminates with an intramolecular [2+2] photocycloaddition that serves to support the proposed biosynthetic origins of 1 from 2.     

Hyphenated techniques in anticancer drug monitoring. I. Capillary gas chromatography-mass spectrometry

Muramic acid (Mur) is present in the cell wall of Eubacteria and serves as a chemical marker for the trace detection of bacteria and bacterial cell wall debris in complex matrices. There have been numerous studies using a variety of derivatives of Mur, particularly in combination with gas chromatography-tandem mass spectrometry (GC-MS-MS) where the detection limit has been steadily lowered. A stable, halogenated derivative, the pentafluorobenzyl oxime (PFBO) acetate of Mur, has been developed by others and successfully used for GC with electron-capture detection. The current report is the first use of this derivative for GC-MS-MS analysis of Mur, or indeed any other carbohydrate, using negative ion chemical ionization (NICI) with GC-MS-MS. Mur was readily detected in settled surface dust (166 ng/mg), as well as dust collected from indoor air (1.4-5.9 ng/mg). Analyses of Mur as a PFBO acetate by GC-NICI-MS-MS or as alditol acetates by electron impact GC-electron impact ionization MS-MS serve as complementary approaches for trace detection in complex matrices.     

Synthesis of a Monophosphoryl Derivative of Escherichia coli Lipid A and Its Efficient Coupling to a Tumor‐Associated Carbohydrate Antigen

Monophosphoryl lipid A is a safe and potent immunostimulant and vaccine adjuvant, which is potentially useful for the development of effective carbohydrate‐based conjugate vaccines. This paper presents a convergent and efficient synthesis of a monophosphoryl derivative of E. coli lipid A that has an alkyne functionality at the reducing end, which is suitable for coupling with various molecules. The coupling of this derivative to an N‐modified analogue of tumor‐associated antigen GM3 through click chemistry is also presented.     

Influence of saccharide size on the cellular immune response to glycopeptides

Glycopeptides that bind to MHC molecules on antigen presenting cells may elicit carbohydrate selective T cells. In order to investigate how the cellular immune response depends on the size of the carbohydrate moiety, a trigalactosylated derivative of an immunogenic peptide from hen egg-white lysozyme (HEL52-61) was prepared. Synthesis was accomplished by assembly of an alpha-1,4-linked trigalactose peracetate which was coupled to Fmoc serine. After activation as a pentafluorophenyl ester the resulting building block was used in solid-phase synthesis In contrast to the corresponding mono- and digalactosylated derivatives of HEL52-61, the trigalactosylated HEL52-61 was not immunogenic. Somewhat surprisingly, this was found to be because the trigalactosyl derivative bound approximately two orders of magnitude weaker to I-Ak MHC molecules than the mono- and digalactosyl peptides. Our observation suggests an explanation for previous findings, which show that glycopeptides isolated from MHC molecules in nature usually carry small saccharides.     

Carbohydrate-metallocene conjugates: selective formation of a zirconadioxacyclopentane-type dimer from the reaction of a bis(enolate)ZrCp2 reagent with a glucofuranoside derivative

The zirconocene enolate complex bis(2-propenolato)ZrCp2 (1) reacts with two molar equivalents of the 1,2,3,4-O-tetramethyl-alpha-D-glucopyranoside (2) with liberation of two equivalents of acetone to yield cleanly the bis(carbohydrate)zirconcene complex (3). Alternatively 1 and the "bifunctional" glucose derivative 3-O-benzyl-1,2-O-isopropylidene-glucofuranoside (4) react to the corresponding zirconadioxacyclopentane-type metallacyclic product that was isolated as the respective dimer (5) featuring a sequence of linearly anellated five-, four-, five-membered metallacycles. Both carbohydrate zirconocene complexes 3 and 5 were characterized by NMR experiments as well as by X-ray diffraction.     

Synthesis of isogranulatimides A and B analogues possessing a 7-azaindole unit instead of an indole moiety

The synthesis of a new family of isogranulatimides analogues is described in which a 7-azaindole replaces the indole moiety. The key step is the photocyclization of the aza didemnimide intermediates which leads to two isomeric analogues of isogranulatimides A and B. A derivative bearing a carbohydrate part linked to the azaindole via a β-N-glycosidic bond was also prepared.     

Synthesis of Sulfur-Containing Analogues of αGalNAc (Tn-Antigen) and βGal1,3αGalNAc (T-Antigen)

Summary.  A method for the preparation of thio-analogues of the T- and Tn-antigen was developed. Thus, starting from a known N-acetamido-glucoside derivative, the epidithio analogue of the Tn-antigen was accessible in a four-step reaction sequence. The corresponding epidithio analogue and the thioanhydro derivative of the T-antigen were synthesized starting from a disaccharide derivative. For the preparation of the epidithio analogue the sulfur atoms were introduced via thiocyanates in a stepwise fashion, using mesylate as the leaving group at C-6 and triflate as the leaving group at C-4 in the reducing carbohydrate moiety. The synthesis of the thioanhydro analogue was achieved by introducing a thiocyanate group at C-6 into the glucose moiety, followed by subsequent displacement of a mesylate group at C-4 under inversion of configuration utilizing sodium methoxide. Received October 16, 2001. Accepted November 7, 2001