Synthesis and DFT-NMR-guided structure revision of cremenolide.

The structure of an anti-plant pathogenic and plant growth-promoting nonenolide, namely cremenolide, was revised by an efficient combination of DFT-based theoretical NMR calculations and synthesis of a target diastereomer. Initially, the planar structure of cremenolide was reconsidered by an individual analysis of the reported NMR spectra. Subsequently, the relative configuration was predicted using NMR calculations of all possible diastereomers based on the ωB97X-D functional.

Sulfoquinovosylglyceryl ether, a new group of ether lipids from lake ball-forming green alga Aegagropilopsis moravica (family Pithophoraceae).

Ether lipids are a minor group of glycerolipids but widespread in nature, playing a vital function as membrane lipids, signalling molecules, or buoyant material. We have discovered sulfoquinovosylchimyl alcohol (1), a sulfonate-substituted glyceroglycolipid, from a lake ball-forming green alga Aegagropilopsis moravica (family Pithophoraceae), with the guidance of antimicrobial activity. The structure of 1, including absolute configurations of all sterogenic centers, was established by extensive NMR analysis, chemical degradation studies, and finally by total synthesis.

Studies on analogs of DAMASCENOLIDETM: Part 4. Synthesis and odor evaluation of sulfur-containing analogs of DAMASCENOLIDETM.

DAMASCENOLIDETM [1, 4-(4-methylpent-3-en-1-yl)furan-2(5H)-one], which is isolated from damask rose, is a useful aroma compound with a citrus-like odor. We have previously reported on the synthesis and odor properties of 34 analogs of 1 as part of our new aroma compound development project. In order to develop better aroma compounds and to gather more information on structure-odor relationships, 6 novel sulfur-containing analogs of 1 were synthesized.

Studies on analogs of DAMASCENOLIDETM: Part 3. Synthesis and odor evaluation of dimethylated, cyclopropanated, and other analogs of DAMASCENOLIDETM.

DAMASCENOLIDETM [1, 4-(4-methylpent-3-en-1-yl)furan-2(5H)-one], which has a citrus-like odor, is an important aroma component of roses. We have previously reported on the synthesis and odor evaluation of 24 analogs of 1 as part of our new aroma compound developing project. To accumulate more information on structure-odor relationships, 10 more promising analogs such as dimethylated and cyclopropanated analogs were synthesized and subjected to odor evaluation.

Enantioselective synthesis and stereochemical determination of the highly reduced polyketide ishigamide.

Ishigamide was isolated as a metabolite of a recombinant strain of Streptomyces sp. MSC090213JE08 and its unsaturated fatty acid moiety has been confirmed in vitro to be synthesized by a type II PKS. Biosynthesis of such a highly reduced polyketide by a type II PKS is worthy of note.

Synthesis of both enantiomers of lycoperdic acid, an unusual mushroom-derived amino acid.

An efficient synthesis of both enantiomers of lycoperdic acid, a 4-hydroxyglutamic acid derivative from edible mushroom Lycoperdon perlatum, was achieved from a chiral aminoalcohol. The key steps were a stereoselective introduction of a C3 unit into a bicyclic ketone and oxidative cleavage of a cyclic vicinal diol into a dicarboxylic acid. This report provides the first synthesis of (-)-lycoperdic acid.

Novel glucoamylase-resistant gluco-oligosaccharides with adjacent α-1, 6 branches at the non-reducing end discovered in Japanese rice wine, sake.

Sake, a traditional Japanese rice wine, contains various oligosaccharides (Sake oligosaccharides; SAOs) derived from rice starch. We previously found that SAOs reach a high degree of polymerization (DP). In this study, we developed a hydrophilic interaction liquid chromatography-time-of-flight/mass spectrometry (HILIC-TOF/MS) based analytical method to separate isomeric SAOs.

Analog synthesis of DAMASCENOLIDE, an important aroma component of roses, and their odor properties.

DAMASCENOLIDE [, 4-(4-methylpent-3-en-1-yl)furan-2(5)-one], which has a citrus-like odor, is an important aroma component of roses. We have previously reported on the synthesis and odor evaluation of double-bond isomers of and concluded that the position and the geometric isomerism of the double-bond had a significant effect on the odor. For the purpose of deepening knowledge about structure-odor relationships, we synthesized 13 analogs of compound and evaluated their odors.

Transglycosylation Forms Novel Glycoside Ethyl α-Maltoside and Ethyl α-Isomaltoside in Sake during the Brewing Process by α-Glucosidase A of .

Sake, the Japanese rice wine, contains a variety of oligosaccharides and glucosides produced by fungal enzymes during the brewing process. This study investigates the effect of knocking out the α-glucosidase () gene on the transglycosylation products in brewed sake. In addition to α-ethyl glucoside and α-glyceryl glucoside, the amount of two compounds that have molecular mass values similar to that of ethyl maltose decreased by gene knockout.

Prediction of the structure of a novel amylopectin-based Cd-associated molecule in the stem of common reed grown in the presence of Cd.

We previously found a novel Cd-associated molecule with an apparent molecular weight of 10-50 kDa in common reeds grown in the presence of Cd. The partial structure of this molecule was predicted by enzymatic digestion to release Cd from a trace amount that had been partially purified from the cell sap. The major component was branched α-glucan, whereas a peptide, β-1,4 glucan, and mannose were found as minor components.

Cucumis sativus secretes 4'-ketoriboflavin under iron-deficient conditions.

A new compound in cucumber, Cucumis sativus, nutrient solution that appears under iron-deficient conditions, but not under ordinary culture conditions, has been revealed by HPLC analysis. The chemical structure of this compound was identified using LC-MS and NMR techniques as that of 4'-ketoriboflavin. This is the first report to show that 4'-ketoriboflavin can be found in metabolites from organisms.

Determination of strain-specific wall teichoic acid structures in Lactobacillus plantarum reveals diverse α-D-glucosyl substitutions and high structural uniformity of the repeating units.

The structural diversity of wall teichoic acid (WTA) was investigated using biochemical and NMR analyses among 19 strains of Lactobacillus plantarum, of which seven were previously established to contain a glycerol-type backbone, whereas the remaining 12 strains possess ribitol-containing WTA. Despite the fact that the WTAs consisted of identical components, namely phosphoric acid, alditol (glycerol or ribitol) and glucose, comparative analysis of the (1)H and (13)C NMR spectra indicated the presence of six different structures, based on the observed differences in the anomeric signals of glucose residues. To determine the six WTA structures, their repeating units were prepared by alkaline hydrolysis, followed by fractionation on HPLC, and analysis by NMR spectroscopy using synthetic molecules as a reference.

Structure-activity relationship of α hormones, the mating factors of phytopathogen Phytophthora.

The mating hormones α1 and α2 induce sexual reproduction of the phytopathogenic genus Phytophthora. To demonstrate the structural elements responsible to hormonal activity, 17 derivatives of α1 and α2 were synthesized and their hormonal activity (oospore-inducing activity) was evaluated. The terminal ester derivatives of α1 (diacetate and dibenzoate) retained the hormonal activity, whereas a dicarbamate derivative completely suppressed the activity.

The second Phytophthora mating hormone defines interspecies biosynthetic crosstalk.

The heterothallic species of the agricultural pest Phytophthora use mating hormones α1 and α2 to regulate their sexual reproduction. Here we describe the absolute stereostructure of the second mating hormone α2 as defined by spectroscopic analysis and total synthesis. We have uncovered not only the interspecies universality of α hormones but also the pathway by which α2 is biosynthesized from phytol by A2-mating type strains and metabolized to α1 by A1 strains.

Synthesis of (2RS,8R,10R)-YM-193221 and an improved approach to tyroscherin, bioactive natural compounds from Pseudallescheria sp.

Short-step syntheses of (2RS,8R,10R)-YM-193221 (1) and tyroscherin (2), which are biologically active compounds isolated from Pseudallescheria sp., were accomplished in six and eight steps from L-tyrosine. The relative stereochemistry of natural YM-193221 was determined to be 8R*,10R*.

Comparison of components and synthesis genes of cell wall teichoic acid among Lactobacillus plantarum strains.

The contents, components, and synthesis genes of cell wall teichoic acid (WTA) in 18 strains of Lactobacillus plantarum were compared. The WTA of each strain was classified by its components as being either the glycerol- or the ribitol-type. The different strains in the WTA type showed marked differences also in two gene regions, tagD1-tagF2 and lp_1816-tagB2, as for the presence or absence, nucleotide sequences, and transcriptional activities.

Structures of two monomeric units of teichoic acid prepared from the cell wall of Lactobacillus plantarum NRIC 1068.

The cell wall of Lactobacillus plantarum contains large amounts of cell wall teichoic acid (WTA). WTA was isolated from the cell wall of L. plantarum NRIC 1068 (= ATCC 8014 and 17-5) by extraction with trichloroacetic acid, and two monomeric units (F1 and F2) were prepared from the alkaline hydrolysate of WTA.

A simple synthesis of four stereoisomers of roseoside and their inhibitory activity on leukotriene release from mice bone marrow-derived cultured mast cells.

Four stereoisomers of roseoside (vomifoliol glucosides) were synthesized using glucose as a chiral resolving reagent. The four synthetic stereoisomers exhibited inhibitory activity on leukotriene release from mouse bone marrow-derived cultured mast cells (BMCMC). The (6S)-isomers of roseoside were about twice as active as (6R)-isomers.

Synthesis and stereochemistry-activity relationship of small bacteriocin, an autoinducer of the symbiotic nitrogen-fixing bacterium Rhizobium leguminosarum.

The four stereoisomers of small bacteriocin, an autoinducer of the symbiotic nitrogen-fixing bacterium Rhizobium leguminosarum, were synthesized via a versatile methodology for 3'-hydroxyacyl homoserine lactones based on the Nagao asymmetric aldol reaction. The synthetic isomers were much less effective at inhibiting the growth of R. leguminosarum RBL5523 than the natural isomer, showing the importance of stereochemistry for activity.

Synthesis and absolute configuration of hormone alpha1.

An important biological event in phytopathogens of the genus Phytophthora is sexual reproduction, which is conducted by two mating types, A1 and A2. A factor known as hormone alpha1 is secreted by the A1 mating type and induces the formation of sexual spores (oospores) in the A2 mating type. Here we describe the asymmetric synthesis and assignment of the absolute configuration of hormone alpha1 by oospore-inducing assays of the synthesized isomers.

Efficient and stereo-selective syntheses of three stereoisomers of the sex pheromone of the cowpea weevil, Callosobruchus maculatus.

An efficient and stereoselective synthesis of three stereoisomers of the sex pheromone of the cowpea weevil, Callosobruchus maculatus, is reported.

Asymmetric total synthesis of ent-sandaracopimaradiene, a biosynthetic intermediate of oryzalexins.

An asymmetric total synthesis of ent-sandaracopimaradiene, a biosynthetic intermediate of oryzalexins, via B-alkyl Suzuki-Miyaura coupling and Lewis acid-mediated B-ring formation as key steps was achieved.

Direct determination of the stereoisomeric composition of callosobruchusic acid, the copulation release pheromone of the azuki bean weevil, Callosobruchus chinensis L., by the 2D-Ohrui-Akasaka method.

The stereoisomeric composition of the copulation release pheromone of the azuki bean weevil, Callosobruchus chinensis L., was determined to be R:S=3.3-3.

DFT studies of the role of C-2-O-2 bond rotation in neighboring-group glycosylation reactions.

Although the synthetic utility of the 1,2-trans relationship of the products of neighboring group participation is well established, it is still common to find glycosylation reactions where the stereochemical purity of the products is not 100%. As part of an ongoing series of density functional theory (DFT) studies of the factors that affect glycosylation reactions which are aimed at allowing synthetic chemists to achieve such selectivities, the structures of four oxacarbenium ions and eight methanol complexes of these ions were optimized for the prototypical ions 2-O-acetyl-3,4,6-tri-O-methyl-D-gluco- (1) and mannopyranos-1-yl (2). These studies corroborate the two-conformer hypothesis and further demonstrate that glycopyranosyl oxacarbenium ions exhibit facial selectivity that depends on, besides the inherent steric and Van der Waals effects, the conformational effect associated with the change from sp(2) to sp(3) hybridization at C-1 during nucleophilic attack and H-bonding between the incoming nucleophile and the electronegative atoms of the electrophile.

Investigations into the role of oxacarbenium ions in glycosylation reactions by ab initio molecular dynamics.

We present a constrained ab initio molecular dynamics method that allows the modeling of the conformational interconversions of glycopyranosyl oxacarbenium ions. The model was successfully tested by estimating the barriers to ring inversion for two 4-substituted tetrahydropyranosyl oxacarbenium ions. The model was further extended to predict the pathways that connect the (4)H(3) half-chair conformation of 2,3,4,6-tetra-O-methyl-d-glucopyranosyl cation to its inverted (5)S(1) conformation and the (4)H(3) half-chair conformation of 2,3,4,6-tetra-O-methyl-d-mannopyranosyl cation to its inverted (3)E conformation.