Synthesis of the A/D/E-ring Core Compounds of Maoecrystal V†.

Synthesis of the A/D/E-ring core compounds of maoecrystal V was achieved. The key Diels-Alder reactions between tricyclic α-methylene lactones and Kitahara-Danishefsky dienes afforded the spirocyclic core compounds in a regioselective and stereoselective manner.

Enantioselective synthesis of the aglycone of burnettramic acid A.

Enantioselective total synthesis of the aglycone of burnettramic acid A, an antifungal pyrrolizidinedione with a terminally mannosylated long acyl chain produced by Aspergillus fungi, has been achieved from a known carboxylic acid by a 14-step sequence. The key steps include 2 types of asymmetric alkylation, coupling of an acetylide intermediate with (S)-epichlorohydrin to provide an acetylenic epoxide in 1 pot, and the Birch reduction to effect desulfonylation, semi-reduction of triple bond, and debenzylation in a concurrent manner. Good agreement of the synthetic aglycone with naturally occurring one in 1H and 13C nuclear magnetic resonance (NMR) spectra, coupled with previously reported unambiguous stereochemical assignment of the sugar moiety, has confirmed the structure of burnettramic acid A.

Overview of Kenji Mori's pheromone synthesis series.

It was the late Professor Kenji Mori, the giant of pheromone synthesis and pioneer of pheromone stereochemistry, who laid the foundation for the practical application of insect pheromones, which play an important role in Integrated Pest Management, one of the key concepts of agriculture in the 21st century. Therefore, it would be meaningful to retrace his achievements at this time, three and a half years after his death. In this review, we would like to introduce some of his notable synthetic studies from his and reconfirm his contributions to the development of pheromone chemistry and their impacts on natural science.

Total Synthesis of the Broad-Spectrum Antibiotic Amycolamicin.

The total synthesis of the antibiotic amycolamicin with a hybrid molecular architecture composed of five ring systems, which exhibits potent antibacterial activity against a wide range of drug-resistant bacteria, has been achieved in a convergent manner. A protecting-group-free intramolecular Diels-Alder reaction of a hydroxy tetraenal intermediate promoted by two equivalents of EtAlCl, which proceeds highly diastereoselectively via an -equatorial transition state, has been utilized to construct the -decalin moiety of the molecule. The full structure of amycolamicin was assembled by a completely stereoconvergent N-acylation of a northern -glycoside unit (α-anomer/β-anomer = 1:1.

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.

Seven-Step Total Synthesis of Sporothriolide.

An enantioselective total synthesis of sporothriolide, a bioactive furofurandione-type fungal metabolite, has been achieved in a 21% overall yield from a commercially available β,γ-unsaturated carboxylic acid via seven steps. The key steps of this synthesis include a highly diastereoselective Michael addition of a chiral oxazolidinone derivative to a nitro olefin, the exploitation of an aromatic ring as a masked carboxylic acid functionality, and the base-promoted elimination of nitrous acid to install the α-methylene lactone unit of sporothriolide in the final step.

Semipinacol rearrangement of a bicyclo[7.2.0]undecane framework into a bicyclo[6.3.0]undecane skeleton: a model study on the biosynthesis of seiridiasteriscane A.

Seiridiasteriscane A is an asteriscane-type sesquiterpenoid bearing a trans-fused bicyclo[6.3.0]undecane skeleton.

Synthesis of a plasmenylethanolamine.

A concise synthesis of a plasmenylethanolamine (PlsEtn-[16:0/18:1 n-9]), known as antioxidative phospholipids commonly found in cell membranes, has been achieved from an optically active known diol through 8 steps. The key transformations for the synthesis of PlsEtn-[16:0/18:1 n-9] are (1) regio- and Z-selective vinyl ether formation via the alkylation of a lithioalkoxy allyl intermediate with an alkyl iodide, and (2) a one-pot phosphite esterification-oxidation sequence to construct the ethanolamine phosphonate moiety in the presence of the vinyl ether functionality. The piperidine salt of synthetic PlsEtn-[16:0/18:1 n-9] was desalinated through reversed-phase high-performance liquid chromatography purification.

Unexpected reversal of stereochemistry observed in the addition of methallyltrimethylsilane to a chiral α-keto imide.

A Lewis acid-promoted nucleophilic addition of methallyltrimethylsilane to a chiral α-keto imide proceeded with stereoselectivity opposite to that predicted from Soai's report. The difference in the structure of α-keto imides between Soai's and our cases might have affected the diastereofacial selectivity.

Synthesis of (12R,13S)-pyriculariol and (12R,13S)-dihydropyriculariol revealed that the rice blast fungus, Pyricularia oryzae, produces these phytotoxins as racemates.

Synthesis of assumed natural (12R,13S)-enantiomers of pyriculariol (1) and dihydropyriculariol (2), phytotoxins isolated from rice blast disease fungus, Pyricularia oryzae, was achieved using Wittig reaction or microwave-assisted Stille coupling reaction as the key step. The synthesis revealed that the natural 1 and 2 are racemates. Foliar application test on a rice leaf indicated that both the salicylaldehyde core and side chain were necessary for phytotoxic activity.

Stereocontrolled Total Synthesis of (-)-Isocelorbicol and Its Elaboration to Natural Dihydro-β-agarofuran Esters.

The first total synthesis of four naturally occurring dihydro-β-agarofuran esters has been accomplished via a highly stereocontrolled 14-step access to their common core triol, (-)-isocelorbicol. A semipinacol rearrangement of an epoxy alcohol to install a quaternary carbon, diastereoselective conjugate reduction of a spirocyclic butenolide for the establishment of a methyl-bearing chiral center, and ring-closing metathesis to construct the decalin ring system were exploited as the key steps for the high-yielding synthesis of (-)-isocelorbicol.

Stereoselective Syntheses of all the Possible Stereoisomers of Coronafacic Acid.

An efficient and stereoselective syntheses of all the possible stereoisomers of coronafacic acid (CFA) has been developed. The stereochemistries of C3a and C7a were controlled in a diastereoselective Diels-Alder type cycloaddition using a chiral auxiliary. CFA and 6--CFA were synthesized by hydrogenation of a common intermediate.

Isolation and structural elucidation of unique γ-oryzanol species in rice bran oil.

Even though γ-oryzanol (OZ) such as 24-methylenecycloartanyl ferulate (24MCAFA) is abundant in purified rice bran oil, we realized that the oil contained the prospect of two additional novels of OZ species. To identify this, we isolated and analyzed their chemical structures by using HPLC-UV-MS, NMR, and IR. We revealed for the first time that the oil had also contained cyclobranyl ferulate (CBFA) and cyclosadyl ferulate (CSFA) which are likely to be exist due to the isomerism of 24MCAFA under acid condition.

Synthesis of Strophasterols C, E, and F.

The synthesis of strophasterols C, E, and F has been accomplished from a 14,15-secoergostane derivative via a 1,3-dipolar cycloaddition of a nitrile oxide intermediate to simultaneously install an isolated cyclopentane ring and a C23 oxygen functionality in a diastereoselective manner and a regio- and diastereoselective selenohydroxylation of an olefinic intermediate under thermodynamic conditions. This synthesis also enabled the stereochemical confirmation of strophasterol C.

Author Correction: Definitive evidence of the presence of 24-methylenecycloartanyl ferulate and 24-methylenecycloartanyl caffeate in barley.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Total Synthesis of Diocollettines A via an Acid-Promoted Oxa-Michael-Aldol-Acetalization Cascade.

A diastereo- and enantioselective total synthesis of diocollettines A with an unusual oxygen-containing tricyclic ring system has been achieved in 63% overall yield from commercially available 3-phenylpropanal via four steps. The key feature of the present synthesis is an exclusively diastereoselective cascade sequence composed of a -selective oxa-Michael addition of 1,3-dihydroxyacetone to a 2,3-dihydropyrylium ion intermediate, intramolecular aldol-type reaction, and intramolecular acetalization.

Analysis of oxidation products of α-tocopherol in extra virgin olive oil using liquid chromatography-tandem mass spectrometry.

When α-tocopherol (α-Toc) exerts its antioxidative effect, a portion of α-Toc is converted to certain oxidation products. Although accumulation of such oxidation products is considered to cause a deterioration in the quality of foods, their distribution and generation in food samples have been still unknown. In this study, we tried to analyze α-Toc hydroperoxide (Toc-OOH) stereoisomers and tocopherylquinone (TQ) in extra virgin olive oil (EVOO) using liquid chromatography-tandem mass spectrometry.

Definitive evidence of the presence of 24-methylenecycloartanyl ferulate and 24-methylenecycloartanyl caffeate in barley.

γ-Oryzanol (OZ), which has a lot of beneficial effects, is a mixture of ferulic acid esters of triterpene alcohols (i.e., triterpene alcohol type of OZ (TTA-OZ)) and ferulic acid esters of plant sterols (i.

4--methylascochlorin stabilizes hypoxia-inducible factor-1 in a manner different from hydroxylase inhibition by iron chelating or substrate competition.

Hypoxia-inducible factor-1 (HIF-1) is a transcription factor that plays essential roles in human diseases including cancer. The synthetic ascochlorin derivative 4--methylascochlorin stabilizes HIF-1α protein, and activates its transcriptional activity, resulting to induce gene expression of its downstream targets such as and . Here, we quantified protein level of HIF-1α in human osteosarcoma U2OS cells treated with ascochlorin-related compounds and typical HIF-1α stabilizers to characterize properties of HIF-1α stabilization by 4--methylascochlorin.

Ktedonoketone and 2'-oxosattabacin, benzenoid metabolites from a thermophilic bacterium Thermosporothrix hazakensis in the phylum Chloroflexi.

A thermophilic bacterium Thermosporothrix hazakensis NBRC 105916 which belongs to the class Ktedonobacteria was investigated to explore its biosynthetic potential of secondary metabolites. UV-guided fractionation led to the identification of a new benzenoid metabolite designated ktedonoketone (6) and an α-diketone metabolite 2'-oxosattabacin (7) along with five known compounds. Compound 7 was previously described as a synthetic compound, but this is the first finding as a natural product.

Unified total synthesis of amorfrutins A and C via the Claisen rearrangement.

A concise, unified total synthesis of the two prenylated aromatic polyketides amorfrutins A and C, which exhibit various medicinally important biological profiles such as antimicrobial, PPARγ modulating and quorum sensing inhibitory activities, has been achieved from commercially available 3,5-dimethoxybenzaldehyde in 38% and 10% overall yields through nine and ten steps, respectively. The key transformation for the synthesis of amorfrutin A was the Claisen rearrangement of a mono--(1,1-dimethylallyl)resorcinol derivative to install the C3-prenyl substituent, while that for the synthesis of amorfrutin C was the double Claisen rearrangement of a di--(1,1-dimethylallyl)resorcinol derivative to introduce the two prenyl groups at the C3 and C5 positions all at once.

Evaluation of lipid oxidation mechanisms in beverages and cosmetics via analysis of lipid hydroperoxide isomers.

Understanding of lipid oxidation mechanisms (e.g., auto-oxidation and photo-oxidation) in foods and cosmetics is deemed essential to maintain the quality of such products.

Synthesis of the N-Acyl Amycolose Moiety of Amycolamicin and Its Methyl Glycosides.

The N-acyl amycolose moiety incorporated in amycolamicin, a broad-spectrum antibacterial natural product produced by soil actinomycetes, and its two anomeric methyl glycosides have been synthesized enantioselectively each in 12 steps from a known methyl ( R)-lactate derivative by exploiting a diastereoselective nucleophilic addition of a p-methoxybenzyloxy-substituted vinyllithium reagent to an α,β-bisalkoxy ketone intermediate to provide the corresponding tertiary alcohol as a single diastereomer. The three sugar derivatives are known as cytotoxic degradation products of amycolamicin.