3945-28-6

Despite of proven efficacy and well tolerability, albomycin is not used clinically due to scarcity of material. Several attempts have been made to increase the production of albomycin by chemical or biochemical methods. In the current study, we have synthesized the active moiety of albomycin δ1 and investigated its binding mode to its molecular target seryl-trna synthetase (SerRS). In addition, isoleucyl and aspartyl congeners were prepared to investigate whether the albomycin scaffold can be extrapolated to target other aminoacyl-tRNA synthetases (aaRSs) from both class I and class II aaRSs, respectively. The synthesized analogues were evaluated for their ability to inhibit the corresponding aaRSs by an in vitro aminoacylation experiment using purified enzymes. It was observed that the diastereomer having the 5′S, 6′R-configuration (nucleoside numbering) as observed in the crystal structure, exhibits excellent inhibitory activity in contrast to poor activity of its companion 5′R,6′S-diasteromer obtained as byproduct during synthesis. Moreover, the albomycin core scaffold seems well tolerated for class II aaRSs inhibition compared with class I aaRSs. To understand this bias, we studied X-ray crystal structures of SerRS in complex with the albomycin δ1 core structure 14a, and AspRS in complex with compound 16a. Structural analysis clearly showed that diastereomer selectivity is attributed to the steric restraints of the active site of SerRS and AspRS.

Abstract: A continuous flow procedure for the synthesis of methyl glycosides (Fischer glycosylation) of various monosaccharides using a heterogenous catalyst has been developed. In-depth analysis of the isomeric composition was undertaken and high consistency with corresponding results observed under microwave heating was obtained. Even in cases where addition of water was needed to achieve homogeneity—a prerequisite for the flow experiments—no detrimental effect on the conversion was found. The scalability was demonstrated on a model case (mannose) and as part of the target-oriented synthesis of d-glycero-d-manno heptose, both performed on multigram scale.

Albomycins are peptidyl thionucleoside natural products that display antimicrobial activity against clinically important pathogens. Their structures are characterized by a thioheptose with atypical stereochemistry including a d-xylofuranose ring modified with a d-amino acid moiety. Herein it is demonstrated that AbmH is a pyridoxal 5′-phosphate (PLP)-dependent transaldolase that catalyzes a threo-selective aldol-type reaction to generate the thioheptose core with a d-ribofuranose ring and an l-amino acid moiety. The conversion of l-to d-amino acid configuration is catalyzed by the PLP-dependent epimerase AbmD. The d-ribo to d-xylo conversion of the thiofuranose ring appears according to gene deletion experiments to be mediated by AbmJ, which is annotated as a radical S-adenosyl-l-methionine (SAM) enzyme. These studies establish several key steps in the assembly of the thioheptose core during the biosynthesis of albomycins.

The present application relates to triterpene glycoside saponin-derived adjuvants, syntheses thereof, and intermediates thereto. The application also provides pharmaceutical compositions comprising compounds of the present invention and methods of using said compounds or compositions in the treatment of and immunization for infectious diseases.

Random copolymers of ?-caprolactone with O-benzyl-protected 4-hydroxy- or 2,4-dihydroxy-δ-valerolactone after hydrogenation form γ-hydroxy functionalized polyesters that degrade via the cyclization to γ-butyrolactone fragments without carboxylic acid formation.

We report here the direct formation of the new chemical product trans-2,5-dihydroxy-3-pentenoic acid methyl ester from pentoses using tin-containing silicates as catalysts. The product is formed under alkali-free conditions in methanol at temperatures in the range 140-180 °C. The highest yields are found using Sn-Beta as the catalyst. Under optimised conditions, a yield of 33% is achieved. Purified trans-2,5-dihydroxy-3-pentenoic acid methyl ester was used for co-polymerisation studies with ethyl 6-hydroxyhexanoate using Candida antarctica lipase B as the catalyst. The co-polymerisation yields a product containing functional groups originating from trans-2,5-dihydroxy-3-pentenoic acid methyl ester in the polyester backbone. The reactivity of the incorporated olefin and hydroxyl moieties was investigated using trifluoroacetic anhydride and thiol-ene chemistry, thus illustrating the potential for functionalising the new co-polymers.

Human UDP-xylose synthase (hUXS1) exclusively converts UDP-glucuronic acid to UDP-xylose via intermediate UDP-4-keto-xylose (UDP-Xyl-4O). Synthesis of model compounds like methyl-4-keto-xylose (Me-Xyl-4O) is reported to investigate the binding pattern thereof to hUXS1. Hence, selective oxidation of the desired hydroxyl function required employment of protecting group chemistry. Solution behavior of synthesized keto-saccharides was studied without enzyme via1H and13C NMR spectroscopy with respect to existent forms in deuterated potassium phosphate buffer. Keto-enol tautomerism was observed for all investigated keto-saccharides, while gem-diol hydrate forms were only observed for 4-keto-xylose derivatives. Saturation transfer difference (STD) NMR was used to study binding of synthesized keto-gylcosides to wild type hUXS1. Resulting epitope maps were correlated to earlier published molecular modeling studies of UDP-Xyl-4O. STD NMR results of Me-Xyl-4O are in good agreement with simulations of the intermediate UDP-Xyl-4O indicating a strong interaction of proton H3 with the enzyme, potentially caused by active site residue Ala79. In contrast, pyranoside binding pattern studies of methyl uronic acids showed some differences compared to previously published STD NMR results of UDP-glycosides. In general, obtained results can contribute to a better understanding in binding of UDP-glycosides to other UXS enzyme family members, which have high structural similarities in the active site.

Fisher glycosylation, the oldest but efficient reaction towards alkyl glycosides, suffers nonetheless from lack of selectivity, especially when dealing with pentoses. In this case, a mixture of the four isomers, namely the furanosides and the pyranosides, is formed. According to previous studies, the rate and selectivity of the reaction depend greatly on the reaction time and the temperature. In this report, another factor was evaluated, the introduction of a weak nucleophilic base. Interestingly, addition of pyridine few hours after the reaction has started allowed rapid isomerization of the methyl pentofuranosides into its pyranoside counterparts. The reaction proceeds with great diastereoselectivity using arabinose, ribose, xylose and lyxose as starting pentoses. Corresponding methyl pyranosides were obtained as the sole isomers with yields ranging from 65% to 75%.

The invention relates to the technical field of synthesis of glucoside, and in particular relates to a method for preparing glucoside, which comprises the following steps of: adding alcoholic solution of acid into crystallization mother liquor, from which target glucoside is separated, after Fisher glycosylation, carrying out reflux reaction, generating target glucoside in reaction liquid, and separating target glucoside, wherein Fisher glycosylation is reflux reaction of D-ribose under catalysis of hydrogen chloride; the target glucoside is 1-methyl-beta-D-pyran nuclear glucoside; crystallization mother liquor is re-converted, so that 1-methyl-alpha-D-furan nuclear glucoside, 1-methyl-beta-D-furan nuclear glucoside and 1-methyl-alpha-D-pyran nuclear glucoside are partcly converted into 1-methyl-beta-D-pyran nuclear glucoside, therefore, the yield of 1-methyl-beta-D-pyran nuclear glucoside is increased; the utilization rate of raw materials is increased to a great extent; the production cost is reduced; and the method for preparing glucoside disclosed by the invention is simple to operate, high in yield, strong in repeatability and easy for industrial production.

Two new flavonol g1lycosides were isolated from the leaves of Siparuna gigantotepala. Their structures were determined to be kaempferol 3-O-β-xylopyranosyl-(1→2)-α-arabinofuranoside (1) and kaempferol 3,7-di-O-methyl-4′-O-α-rhamnopyranosyl-(1→2)-β-glucopy

Different solid acid catalysts, which include several zeolites, zirconium oxide based catalysts, and materials that contain sulfonic acids, have been evaluated in the dehydration of xylose to furfural in alcohol media. Alcohol media were selected to reduce side reactions, many of which occur in aqueous media. Among the tested alcohols, 2-propanol provided better results and yielded a higher furfural production than ethanol and methanol. Catalyst screening evidenced that small-pore-size zeolites (H-ZSM5) or catalysts that show weak acidity (tungstated zirconia) were unable to promote the desired transformation. Kinetic studies performed for the different types of materials revealed that the nature of the acid sites influenced the catalytic performance of the different solid acids to the extent of conditioning the main reaction pathway for the transformation of xylose into furfural. Thus, whereas Lewis acids seem to promote furfural production by the direct dehydration of xylose, Br?nsted-type catalysts lead to alkyl xylosides as intermediates in the overall transformation. Although both types of catalysts provide high furfural yields in short reaction times, especially at high temperatures, commercially available β-zeolite with an adequate combination of Br?nsted and Lewis acids sites seems to contain the right physicochemical properties to maximize furfural production.

A minor xylanase, named XYN IV, was purified from the cellulolytic system of the fungus Trichoderma reesei Rut C30. The enzyme was discovered on the basis of its ability to attack aldotetraohexenuronic acid (HexA-2Xyl-4Xyl-4Xyl, HexA3Xyl3), releasing the reducing-end xylose residue. XYN IV exhibited catalytic properties incompatible with previously described endo-β-1,4-xylanases of this fungus, XYN I, XYN II and XYN III, and the xylan-hydrolyzing endo-β-1,4-glucanase EG I. XYN IV was able to degrade several different β-1,4-xylans, but was inactive on β-1,4-mannans and β-1,4-glucans. It showed both exo-and endo-xylanase activity. Rhodymenan, a linear soluble β-1,3-β-1,4-xylan, was as the best substrate. Linear xylooligosaccharides were attacked exclusively at the first glycosidic linkage from the reducing end. The gene xyn4, encoding XYN IV, was also isolated. It showed clear homology with xylanases classified in glycoside hydrolase family 30, which also includes glucanases and mannanases. The xyn4 gene was expressed slightly when grown on xylose and xylitol, clearly on arabinose, arabitol, sophorose, xylobiose, xylan and cellulose, but not on glucose or sorbitol, resembling induction of other xylanolytic enzymes from T. reesei. A recombinant enzyme prepared in a Pichia pastoris expression system exhibited identical catalytic properties to the enzyme isolated from the T. reesei culture medium. The physiological role of this unique enzyme remains unknown, but it may involve liberation of xylose from the reducing end of branched oligosaccharides that are resistant toward β-xylosidase and other types of endoxylanases. In terms of its catalytic properties, XYN IV differs from bacterial GH family 30 glucuronoxylanases that recognize 4-O-methyl-d-glucuronic acid (MeGlcA) substituents as substrate specificity determinants. 2012 The Authors Journal compilation

An improved and practical route for a large-scale synthesis of 2-deoxy-L-ribose starting from L-arabinose has been developed. This is the first reported synthesis of 2-deoxy-L-ribose in which deoxygenation has been mediated by hypophosphite reagents instead of by organotin reagents.

UDP-d-apiose/UDP-d-xylose synthase (AXS) catalyzes the conversion of UDP-d-glucuronic acid to UDP-d-apiose and UDP-d-xylose. An acetyl-protected phosphonate analogue of UDP-d-apiose was synthesized and used in an in situ HPLC assay to demonstrate for the first time the ability of AXS to interconvert the two reaction products. Density functional theory calculations provided insight into the energetics of this process and the apparent inability of AXS to catalyze the conversion of UDP-d-xylose to UDP-d-apiose. The data suggest that this observation is unlikely to be due to an unfavorable equilibrium but rather results from substrate inhibition by the most stable chair conformation of UDP-d-xylose. The detection of xylose cyclic phosphonate as the turnover product reveals significant new details about the AXS-catalyzed reaction and supports the proposed retroaldol-aldol mechanism of catalysis.

A combination of experimental and theoretical methods have been used to elucidate the complexation properties of a new sugar-derived hexadentate ligand, namely methyl 2,3,4-tri-O-(2-picolyl)-β-D-ribopyranoside (L). The coordination bond lengths in the complexes with MnII, Co II, NiII, and ZnII show substantial deviations from ideal octahedra with deformation towards trigonal-prismatic geometries, which is indicative of a conformationally constrained ligand. The metal-cation-ligand interactions were studied for L and the acyclic analogue L' [1,2,3-tri-O-(2-picolyl)-1,2,3-propanetriol] by spectroscopic methods and isothermal calorimetric titrations for the series MnII, Co II, NiII, ZnII, and CuII. The results indicate a stabilization of the complexes obtained with L compared with L', depending on the nature of the metal. Molecular modeling studies showed that the presence of the sugar moiety strongly favors conformations compatible with metal binding, which suggests an entropic origin of the stabilization of L complexes with regards to L' complexes. Moreover, the differences in the metal chelation profiles of L and L' are related to the constraints in the sugar group in the metal-bound structures. This study shows that foreseeing the degree of preorganization of flexible ligands may drive the design of a new generation of chelating compounds. A new sugar-derived ligand, with its coordination site embedded in a pyranoside cycle in the chair conformation, has been designed. Its transition-metal complexes were characterized by experimental and complexation methods and revealed a dramatic impact of the preorganization and complementarity of the carbohydrate scaffold on the metal binding.

Chemical analysis of the Indonesian soft coral Sinularia sp. (order Alcyonacea, family Alcyoniidae) afforded a known glucosylcerebroside of the sarcoehrenoside-type and sinularioside (2), a new naturally triacetylated glycolipid containing two α-d-arabinopyranosyl residues and a myristyl alcohol unit. Their complete stereostructures were solved by interpretation of MS and NMR data along with CD analysis of degradation products. Sinularioside proved to moderately inhibit LPS-induced NO release, providing interesting clues into the poorly understood structure-activity relationships for anti-inflammatory glycolipids.

An effective application development of the polysaccharide ulvan requires a comprehensive knowledge about the influence of the extraction process on composition of the extracts and in ulvan itself. In this context, the two main objectives of the present work are (1) the establishment of an efficient extraction process for ulvan and (2) development of an accurate characterization methodology to evaluate the extract composition and ulvan content. Three ulvan-rich extracts obtained by different schemes of extraction were studied. The methodology for the analysis was improved and a detailed analysis of extracted ulvan was provided. The polysaccharide is rich in ulvanobiuronic acid 3-sulfate type A [→4)-β-d-GlcAp-(1 → 4)-α-l-Rhap 3S-(1→], with minor amounts of ulvanobiuronic acid 3-sulfate type B [→4)-α-l-IdoAp-(1 → 4)-α-l-Rhap 3S-(1→]. The extract with the higher degree of purification is a high molecular weight polysaccharide (790 kDa) composed of rhamnose (22.4%), glucuronic acid (22.5%), xylose (3.7%), iduronic acid (3.1%) and glucose (1.0%). It is highly sulfated (32.2%) and contains 1.3% of proteins and 10.3% of inorganic material. Applying simple extraction scheme it was possible to obtain an extract from green algae with high content of ulvan without affecting the overall chemical structure of the polysaccharide.

We report the concise synthesis of (+)-polyoxamic acid and (+)-5-O-carbamoyl polyoxamic acid from L-xylose in seven or six steps, respectively. The key steps include a diastereoselective amination of syn-1,2-polybenzyl ethers using chlorosulfonyl isocyanate (CSI) and the one-pot introduction of carbamates into the allylic benzyl ether and primary hydroxyl moieties. Georg Thieme Verlag Stuttgart.

The X-ray diffraction analysis, 13C CP MAS NMR spectra and powder X-ray diffraction patterns were obtained for selected methyl glycosides: α- and β-d-lyxopyranosides (1, 2), α- and β-l-arabinopyranosides (3, 4), α- and β-d-xylopyranosides (5, 6) and β-d-ribopyranoside (7) and the results were confirmed by GIAO DFT calculations of shielding constants. In X-ray diffraction analysis of 1 and 2, a characteristic shortening and lengthening of selected bonds was observed in molecules of 1 due to anomeric effect and, in crystal lattice of 1 and 2, hydrogen bonds of different patterns were present. Also, an additional intramolecular hydrogen bond with the participation of ring oxygen atom was observed in 1. The observed differences in chemical shifts between solid state and solution come from conformational effects and formation of various intermolecular hydrogen bonds. The changes in chemical shifts originating from intermolecular hydrogen bonds were smaller in magnitude than conformational effects. Furthermore, the powder X-ray diffraction (PXRD) performed for 4, 5 and 7 revealed that 7 existed as a mixture of two polymorphs, and one of them probably consisted of two non-equivalent molecules.

Montmorillonite K-10-catalyzed Fischer type glycosylation was studied for various monosacharides with different alcohols under microwave irradiation. The method was found to be efficient, economic, simple, and time saving and the catalyst montmorillonite K-10 was reused three times without loss of catalytic activity and anomeric selectivity. With glycerol, the method gave products glycosylated at primary alcohols only.

Pancratistatin is a potent anticancer natural product, whose clinical evaluation is hampered by the limited natural abundance and the stereochemically complex structure undermining practical chemical preparation. Fifteen aromatic analogues of conduritol F, L-chiro-inositol, and dihydroconduritol F that possess four of the six pancratistatin stereocenters have been synthesized and evaluated for anticancer activity. These compounds serve as truncated pancratistatin analogues lacking the lactam ring B, but retaining the crucial C10a-C10b bond with the correct stereochemistry. The lack of activity of these compounds provides further insight into pancratistatin's minimum structural requirements for cytotoxicity, particularly the criticality of the intact phenanthridone skeleton. Significantly, these series provide rare examples of simple aromatic conduritol and inositol analogues and, therefore, this study expands the chemistry and biology of these important classes of compounds.

The total syntheses of DAB1 (1) and (-)-lentiginosine (2) were concisely accomplished from D-lyxose via regioselective and diastereoselective NHCbz introduction using CSI, chemoselective removal of the Cbz protection, and ring-closing metathesis as key steps.

Mixtures containing the majority of partially O-methylated alditol acetates (PMAAs), necessary for the GC-MS based identification of glycosidic linkages in oligo- and polymeric structures were prepared. Rha, Fuc, Rib, Ara, Xyl, Man, Gal, and Glc were converted to their Me glycosides, and the products were progressively O-methylated using the Purdie reagent at 25°C. Resulting PMGs were assayed by TLC and at times that were optimum for formation of mono-O-methyl derivatives and later for higher degrees of methylation; they were converted to PMAAs, in a process incorporating NaB2H4 reduction. The majority of these can be used as standards for simultaneous identification of pyranosides and some furanosyl units particularly in heteropolysaccharides. The relative reactivities of OH-groups were determined by GC-MS as: Me α- and β-Glcp, HO-2 > HO-4 > HO-3 > HO-6, Me α- and β-Galp, HO-3 > HO-2 > HO-4 > HO-6, Me α-Manp, HO-3 > HO-2 > HO-4 > HO-6, Me β-Manp, HO-3 > HO-4 ≥ HO-6 > HO-2, Me α-Rhap, OH-3 > OH-2 > OH-4; Me αβ-Fucp, OH-2 > OH-3 > OH-4, and Me αβ-Xylp, OH-2 > OH-4 > OH-3. The results differ from those obtained with Haworth, Hakomori, and Ciucanu methylation techniques, although some similarities occurred with the more rapid Kuhn method.

The 2,3,4-tri-toluenesulfonate ester derivatives of the methyl pyranosides of L-arabinose, D-ribose, D-lyxose, and D-xylose have been prepared, and their substitution reactions with various nucleophiles have been examined. For arabinose, xylose, and ribose, highly regioselective monosubstitutions were observed with benzoate, nitrite, and azide anions. These reactions have led to short and simple routes from D-xylose to L-arabinose derivatives, from L-arabinose to D-xylose derivatives, and from D-ribose to L-lyxose derivatives. The tritosylate derived from methyl α-D-lyxopyranoside was unreactive toward nucleophilic substitution reactions, giving instead a dihydropyran product arising from an initial E2 elimination reaction of the 2-tosylate.

Structurally novel cyclitols, 1-aryl-1-deoxyconduritols F, were efficiently prepared from D-xylose, utilizing RCM as a key step. Various aromatic residues were incorporated in the cyclitol skeleton with total stereochemical control, utilizing a diastereoselective aryl cuprate addition to a γ-alkoxy enoate. The synthetic route establishes a firm foundation for a practical synthesis of the antitumor alkaloid pancratistatin and its aryl analogues.

Four L-erythro-2-uloses were readily prepared from L-arabinose via a reaction sequence involving Fischer glycosidation, acetalization and oxidation. Bulky steric sensors at the anomeric center could enhance the stereoselectivity of the dioxirane epoxidation and one of the uloses performed with good enantioselectivity towards trans-stilbene (up to 90% ee). However, the catalysts decomposed during the epoxidation and the maximum chemical yield was only 13% under the basic conditions. Three L-threo-3-uloses could overcome the decomposition problem based on the electron withdrawing effect of the ester group(s) α to the ketone functionality. The best chemical yield was up to 93% using a ketone with two flanking ester groups. One of the improved uloses displayed moderate enantioselectivity towards trans-disubstituted and trisubstituted alkenes (40-68% ee).

Novel (2R,4R)- and (2S,4S)-iso dideoxynucleosides with exocyclic methylene have been designed and synthesized, based on the lead BMS-200475 (3) which exhibited potent anti-HBV activity. For the synthesis of D types of (2R,4R)-nucleosides, L-xylose was converted to the key intermediate 14. The intermediate 14 was converted to the uracil derivative 4a and the cytosine derivative 4b. Compound 14 was also converted to the purine derivatives such as adenine derivative 4c, hypoxanthine derivative 4d, and guanine derivative 4e. The corresponding L types of (2S,4S)-enantiomers were more efficiently synthesized from the commercially available 1,2-isopropylidene-D-xylose (20) than the synthetic method used in the synthesis of (2R,4R)-nucleosides. The key intermediate 25 was converted to the pyrimidine analogues 5a and 5b and the purine derivatives 5c, 5d, and 5e using the similar method used in the preparation of 4c, 4d, and 4e. The synthesized final (2R,4R)- and (2S,4S)-nucleosides were tested against several viruses such as HIV-1, HSV-1, HSV-2, HCMV and HBV, (2R,4R)-Adenine analogue 4c exhibited potent anti-HBV activity (EC50 = 1.5 μM in 2.2.15 cells) among compounds tested, while (2R,4R)-uracil derivative 4a was the most active against HCMV among compounds tested and (2R,4R)-adenine derivative 4c was found to be moderately active against the same virus. However, the corresponding (2S,4S)-isomers were found to be totally inactive against all tested viruses. Both (2R,4R)-adenine derivative 4c and (2S,4S)-adenine analogue 5c were totally resistant to the adenosine deaminase like iso-ddA (1). From the molecular modeling study the hydroxymethyl side chains of BMS-200475 (3) and 4c were almost overlapped, indicating that 4c may be suitable for phosphorylation by cellular kinases like the lead 3, but some discrepancy between two bases was observed, indicating why 4c is less potent against HBV than 3. It is concluded that discovery of (2R,4R)-adenine analogue 4c as potent anti-HBV agent suggested that the sugar moiety of this series can be regarded as a novel template for the development of new anti-HBV agent and oxygen atom can be acted as a bioisoster of C-OH. Copyright

L-Ribose was synthesized by a simple four-step method with overall yield of 76.3% from a protected L-arabinose derivative, which is a compatible intermediate for the synthesis of L-deoxyribose. The key step of this strategy is the Swern oxidation and subsequent stereoselective reduction accompanied by inversion of the 2-hydroxy group of protected L-arabinose.

Novel monocyclic L-Nucleoside compounds have the general formula STR1 Embodiments of these compounds are contemplated to be useful in treating a wide variety of diseases including infections, infestations, neoplasms, and autoimmune diseases. Viewed in terms of mechanism, embodiments of the novel compounds show immunomodulatory activity, and are expected to be useful in modulating the cytokine pattern, including modulation of Th1 and Th2 response.

Two new lignan glycosides, 4-O-[α-L-arabinopyranosyl-(1'''→2'')-β-D-xylopyranosyl-(1'''→5'')-β-D-ap iofuranosyl] diphyllin (1), named ciliatoside A (1), and 4-O-{[β-D-apiofuranosyl-(1''''→3''')-α-L-arabinopyranosyl-(1''''→2'')] [β-D-xylopyranosyl-(1''''→5'')]-β-D-apiofuranosyl}diphyllin (2), named ciliatoside B (2), were isolated from the whole plant of Justicia ciliata. The structures of 1 and 2 were determined by spectral and chemical methods. Compounds 1 and 2 strongly inhibited the accumulation of NO2- in lipopolysaccharide-stimulated RAW 264.7 cells in a concentration-dependent manner with IC50 values of 27.1 ± 1.6 and 29.4 ± 1.4 μM, respectively.

The absolute stereostructures of betavulgaroside II having a dioxolane- type substituent and betavulgaroside IV having an acetal-type substituent, which were isolated from the roots of Beta vulgaris L. (sugar beet, Chenopodiaceae) and exhibited hypoglycemic activity on glucose-loaded rats, were determined by the chemical correlations of betavulgarosides II and IV with a known saponin, momordin I. In these chemical correlations, the α-L- arabinopyranosyl moiety of momordin I was converted to a dioxolane-type substituent of betavulgaroside II or to an acetal-type substituent of betavulgaroside IV. Additionally, the 2'-diastereoisomer of betavulgaroside IV was synthesized from momordin I, and four acetal-type substituent analogues were also synthesized from L- and D-arabinose.

Improved synthesis of 2-deoxy-L-ribose and the corresponding 2-deoxy- 3,5-di-O-p-toluoyl-α-L-erythro-pentofuranosyl chloride are described from L- arabinose.

Novel isodideoxy nucleosides with exocyclic methylene were synthesized starting from L-xylose utilizing anomeric demethoxylation, Wittig reaction and Mitsunobu reaction as key steps and evaluated for antiviral activity.

A synthetic route was established for the preparation of [13C2]-4-hydroxy-4H-furo[3,2-c]pyran-2(6H)-one (patulin) to be used in a stable isotope dilution assay. Mass spectral analyses were performed using electron impact ionization (EI), negative electrospray ionization (ESI), collision-induced dissociation (CID), and atmospheric pressure ionization. Fragmentation routes in the EI mode and in CID were concluded and compared with each other.

The product distribution of the iodine-catalyzed methyl glycosidation of four pentoses (D-ribose, D-arabinose, D-xylose, and D-lyxose) and two 6-deoxyhexoses (L-rhamnose, and D-fucose) was studied by HPLC using an APS column (dihydrogen sulphate form) with different acetonitrile-water mobile phases. In agreement with earlier results, a temperature dependent on-column isomerization was observed for all the investigated aid oses, except for ribose. The first-eluted furanosides were followed by pyranosides, and the free sugars were eluted last with the highest retention volumes.

Following the characterization of trigoneosides Ia, Ib, IIa, IIb; IIIa, and IIIb, seven new steroidal saponins called trigoneosides IVa, Va, Vb, VI, VIIb, VIIIb, and IX were isolated from a medicinal foodstuff fenugreek seed, the seeds of Trigonella foenum-graecum L. (Leguminosae) originating from India. The structures of trigoneosides IVa, Va, Vb, VI, VIIb, and VIIIb were elucidated on the basis of chemical and physicochemical evidence.

The absolute stereostructures of betavulgarosides III and IV, which were isolated from the roots of Beta vulgaris L. (sugar beet) and exhibited inhibitory activity on glucose absorption, were determined by the chemical correlation of betavulgaroside IV with a known saponin momordin I, which included the conversion from the α-L-arabinopyranosyl moiety of momordin I to the acidic acetal-type substituent of betavulgarosides III and IV via the α-L-ribopyranosyl derivative. Furthermore, four acidic acetal-type substituent analogues were synthesized from L- and D-arabinose.

Four new methyl ester derivatives of oleanene glycosides (3-6) were isolated from the seeds of Astragalus complanatus R. BR. together with two known triterpene glycosides, astragaloside VIII methyl ester (1) and soyasaponin I methyl ester (2) after treatment with diazomethane during separation procedure. The structures of 3-6 were elucidated as 3-O-α-L-rhamnopyranosyl(1→2)-β-D-xylopyranosyl(1→2)-6-O-methy-β-D- glucuronopyranosyl-soyasapogenol B 22-O-β-D-glucopyranoside, 3-O-α-L-rhamnopyranosyl(1 →2)-β-D-galactopyranosyl(1→2)-6-O-methyl-β-D-glucuronopyranosyl-soy asapogenol B 22-O-β-D-glucopyranoside, 3-O-α-L-rhamnopyranosyl(1→2)-β-D-xylopyranosyl(1→2)-6-O-methyl-β-D -glucuronopyranosyl 3β,22β,24-trihydroxy-11-oxo-olean-12-ene and 3-O-α-L-rhamnopyranosyl (1→2)-β-D-galactopyranosyl(1→2)-6-O-methyl-β-D-glucuronopyranosyl 3β,22β,24-trihydroxy-11-oxo-olean-12-ene, respectively.

Conversion of arabinose 10 to the protected ketone 13 followed by Wittig condensation to 14, acidcatalysed cyclisation (to lactone 16), dehydration and deprotection provides a brief synthesis of the mycotoxic substance patulin 1, which is produced by Penicillium and Aspergillus spp.In a similar manner, the biogenetic precursor to patulin, neopatulin 8, is synthesized from lyxose 25 via the key intermediates 24, 28 and 30.

Under new simplified conditions, the transacetalization reaction from dimethoxymethane leads to new methyleneacetals of arabinose and ribose.These compounds, with only one hydroxyl function are new chiral auxiliaries.The structures were established by high-field NMR. Key words: transacetalization / dimethoxymethane / arabinose / ribose / methyleneacetal

Methyl D-pentofuranosides were prepared by Fischer glycosidation of the aldopentoses D-arabinose, D-lyxose, D-ribose, D-xylose, and 2-deoxy-D-erythro-pentose, and oxidized with O2 over a platinum oxide catalyst to give the corresponding methyl D-pentofuranosiduronic acids. After purification by anion-exchange chromatography, these glycosides were hydrolyzed to give the corresponding D-penturonic acids [D-arabinuronic acid (1), D-lyxuronic acid (2), D-riburonic acid (3), D-xyluronic acid (4), and 2-deoxy-D-erythro-penturonic acid (5)] in 80% yield based on the starting pentofuranoside. 1-13C-Substituted D-aldopentoses were used to prepare D-(1-13C)penturonic acids. Aqueous solutions of the 1-13C-substituted penturonic acids, studied over a range of pH values by 13C-n.m.r. spectroscopy, were found to contain alpha- and beta-furanoses, acyclic aldehyde and hydrate, and/or hydrated 2,5-lactone. The ratio of D-riburonic acid anomers was most sensitive to solution pH (alpha/beta = 0.49 and 1.2 at pH 1.9 and 4.9, respectively). The values of the 1H and 13C chemical shifts, and 1H-1H. 13C-1H, and 13C-13C spin-coupling constants, were determined by 1H-(300, 500, and 620 MHz) and 13C-(75 MHz) n.m.r. spectroscopy with the aid of 2-D 13C-1H chemical shift correlation maps, 2-D 1H-1H COSY data, and 13C substitution, and were compared to those determined previously for structurally-related furanose rings. Isomerization of the penturonic acids at pH 5.0 and 50 degrees gave the corresponding 4-pentulosonic acids.

Key Word Index - Rehmannia glutinosa var. hueichingensis; Scrophulariaceae; iridoid glycosides; iridoid arabinoside; iridoid rutinoside; jioglutosides.Abstract - Two new iridoid glycosides named jioglutosides A and B, together with 11 known iridoid glycosides, have been isolated from the fresh roots of Rehmannia glutinosa var. hueichingensis.On the basis of chemical and spectral analyses, the structures of jioglutosides A and B have been elucidated.

Reduction of tosylhydrazone derivatives of ketones and aldehydes with sodium cyanoborohydride in acidic medium is a mild, albeit versatile, deoxygenation reaction.The reaction mechanism has been proposed to proceed via either a direct hydride attack route or a tautomerization-then-reduction route.By using a mild reduction procedure (NaBH3CN, THF-MeOH, 0 deg C), it has been possible to stop the deoxygenation halfway and isolate the nascent tosylhydrazine product.Characterization of the resulting hydrazine to define the origin of the hydrogen being delivered to theformer carbonyl carbon has allowed us to unambiguously distinguish between these two possible mechanisms.Studies of reduction of tosylhydrazones derived from conjugated and saturated ketones confirmed earlier speculation that these reductions occur through a direct hydride attack mechanism.The reduction of para-substituted methyl phenyl ketone tosylhydrazones revealed a competition between these two mechanisms.Substrates bearing electron-donating substituents prefer to direct hydride attack pathway, while those with electron-withdrawing substituents favor an initial tautomerization prior to reduction.Sugar and hydroxyl ketone tosylhydrazones are also reduced by competing mechanisms.The mechanistic diversity in those cases may be attributed to the inductive effects compelled by the α substituents and the conformational constraints imposed by the ring structure.The mechanistic insights gained from these studies indicate that the direct hydride attack mechanism is the main reaction pathway due to the propensity of NaBH3CN to selectively attack the iminium ion.The tautomerization-then-reduction mechanism prevails only when the tautomerization of hydrazon to azohydrazine is facilitated.

Most of the glycosides examined were smoothly oxidized by the bis-tributyltin oxide-bromine method without protection of the other hydroxyl groups to the mono-oxo derivatives in high yield and with high regioselectivity.The regioselectivity (position of oxidation) can be predicted from two independent rules: anomeric control (the oxidation takes place at C-3 for the glycosides which have an equatorial glycosidic linkage and at C-4 for those which have an axial glycosidic linkage) and axial oxidation for cis-1,2 glycols.Keywords - carbohydrate; glycoside; oxidation; regioselective oxidation; bis-tributyltin oxide-bromine; dibutyltin oxide-bromine; brominolysis; oxo-glycoside; 13C-NMR.

An anthracycline compound (13-deoxycarminomycin) selected from the group consisting of anthracycline compounds represented by the following formula STR1 R1 is a hydroxy group, R2 represents a hydrogen atom or a hydroxyl group, R3 is a hydrogen atom, R4 represents one of the following groups (a) to (d) STR2 and if R2 is hydroxyl, R4 is not (d).

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Fractionation of the active ethanol extract of Desfontainia spinosa based on cytotoxicity has led to the discovery of three new derivatives of the parent compound, 11-deoxocucurbitacin I.The structures of 23,24-dihydro-11-deoxocucurbitacin I and the glycosides, spinosides A and B were elucidated on the basis of extensive analysis of their high field 1H NMR, 13C NMR, high resolution mass spectra (fast atom bombardment, field desorption, chemical ionization, electron impact) and chemical interconversions.Spinosides A and B were cytotoxic in the KB cell culture assay.

The structures of deacetyl Glykenins (DG)-A, B, and C, basic structures of Glykenins, were elucidates by chemical degradation and interpretation of spectral data.

A simple, regioselective O-deacetylation procedure is described which involves > OH > OMe.No acyl migration took place under the reaction conditions.

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