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Regioselective elimination of a vicinal bis-triflate having an adjacent ether oxygen functional group has been developed. Considered in the context of our studies of the regioselective elimination of vicinal dibromide, the key to the mechanism involves the electron-withdrawing inductive effect of the neighboring oxygen functional group. Aliphatic vinyl triflate was shown to be effective in Suzuki–Miyaura cross coupling compared with corresponding aliphatic vinyl bromide.

Regioselective elimination of a vicinal bis-triflate having an adjacent ether oxygen functional group has been developed. Considered in the context of our studies of the regioselective elimination of vicinal dibromide, the key to the mechanism involves the electron-withdrawing inductive effect of the neighboring oxygen functional group. Aliphatic vinyl triflate was shown to be effective in Suzuki–Miyaura cross coupling compared with corresponding aliphatic vinyl bromide.

An environmentally friendly coating method of lipophilic thiols on metal surface is described. Lipophilic thiols were chemically modified to a water-soluble derivative, prepared from lipophilic thiol, succinic linker, and symmetrically branched oligoglycerol. Due to the chemical modification, water was used as a solute of coating reagent. The anticorrosive effect of metal piece with the water-soluble derivative in water was as high as with lipophilic thiol in organic solvent.

Alcohol oxidation is one of the most principal transformations used in organic synthesis. During the development of these oxidation methods, chemoselective oxidation of a specific alcohol in a polyol has enabled the discrimination of multiple hydroxy groups, which can increase the synthetic efficiency by reducing the use of protecting groups. This digest highlights recent topics of the catalytic systems using nitroxyl radicals for the chemoselective alcohol oxidation and the representative examples during the synthesis or derivatization of natural products., ファイル公開：2022-02-20

The asymmetric coupling reaction of 2-hydroxybenzo[c]phenanthrenes by using Cu–chiral diamine under atmospheric air is described. The use of CuCl-(–)-sparteine and CuCl-cyclohexanediamine derivatives was found to be highly effective to give the helical quinone derivatives in a good yield with high percent enantiomeric excess.

We have developed azaadamantane-type nitroxyl radicals (AZADOs) and azabicyclo-type nitroxyl radicals (ABNOs) as highly active alcohol oxidation catalysts. Herein, the electrochemical properties of these nitroxyl radicals were investigated by measuring their formal potentials using cyclic voltammetry (CV). The redox potentials were rationalized with the aid of density functional theory (DFT) calculations. A good correlation between the experimental redox potential and the DFT-computed energy differences (ΔE) between nitroxyl radicals and oxoammonium species was obtained, which shows the effectiveness of DFT in predicting the redox potentials of nitroxyl radicals. Redox potential appears to be an important factor of catalytic activity.

An atropisomeric lactam which was prepared with high enantioselectivity by catalytic asymmetric intramolecular N-arylation, was efficiently converted to synthetic intermediates for NET inhibitors through highly diastereoselective α-alkylation followed by hydration and trans-tert-butylation.

A chiral synthesis of α-hydroxy-H-phosphinates was achieved via lipase-catalyzed hydrolysis of acetate precursors.

The reaction of 3a-benzhydryl-3,3a,4,5-tetrahydro-2H-cyclopenta[b]furan and various 2-alkanols in the presence of a catalytic amount of pyridinium 4-tolunesulfonate in dichloromethane gave 3a-benzhydryl-6a-(1-methyl-aloxy)-hexahydrocyclopenta[b]furan in more than 90% chemical yields. The resulting diastereomeric mixture is easily separable on silica gel chromatography because of the large ΔRf value (briefly 0.1). Absolute configuration of the 2-alkanols can be easily estimated by the chemical shifts of 1H and 13C NMR of methyne group of the benzhydryl moiety.

Polyamine–enediyne conjugates were synthesized and exhibited potent DNA damaging ability under physiological conditions. The extent of their activity was shown to depend upon the polyamine length that regulates the DNA binding affinity of the conjugates, and enhanced DNA damaging activities were observed under slightly acidic conditions.

To investigate the mechanism of stilbene synthase (STS) reaction, the origin of the aromatic protons of resveratrol B-ring was examined using STS from Arachis hypogaea expressed in Escherichia coli and deuterated malonyl CoA. The presence of resveratrol labeled with three deuterium atoms was detected by GCMS analysis indicating decarboxylation earlier than aromatization, i.e. exclusion of intermediacy of stilbenecarboxylic acid in STS reaction.

We describe a highly convergent approach for the synthesis of the tetraglucosyl glucitol 1 and its derivatives 4 , 5 and 6 which exhibit phytoalexin-elicitor activity in rice cells based on sequential glycosylation.

A stereodivergent synthesis of β-amino-α-hydroxy- H -phosphinates was achieved by ALB-catalyzed hydrophosphinylation of N , N -dibenzyl-α-amino aldehydes tuning the chirality of the catalyst.

Development of enediyne model compounds that produce dehydrotoluene diradicals under acidic media is described. The ionic character of the diradicals is shown to be avoided by the electron-withdrawing groups in the molecules both in benzene and MeOH.

The Arabidopsis thaliana genome sequencing project has identified several triterpene synthase homologues. One cDNA of these clones, YUP8H12R.43, was obtained and functionally expressed in yeast. At least nine triterpenes have been identified as its products based on NMR and LCMS analysis. The products include extensively migrated triterpenes, multiflorenol and bauerenol. Several chimeric clones were constructed between YUP8H12R.43 and A. thaliana lupeol synthase LUP1, to reveal that a C-terminal half and a part of N-terminus is important for such product multiplicity. The presence of such multifunctional triterpene synthase in plants is noteworthy from both a mechanistic and a physiological point of view.

Stable α-alkynylacetic acid derivatives related to cis-enediyne were synthesized and the rate of decarboxylative cycloaromatization of 3,5-difluoro derivative 7c was found to be much faster than that of the corresponding phenyl derivative 7a. The cycloaromatization reaction mechanisms of 7c under various conditions were investigated.

A highly stereoselective synthesis of an alkenylated malonic diamide starting from a γ,δ-epoxy-α,β-unsaturated carboxamide was accomplished using the masked acyl cyanide (MAC: the protected hydroxymalonitrile) via palladium-catalyzed regio- and stereoselective carboncarbon bond formation.

N-glycolylation of 3-(diethoxyphosphorothioyl)methyl-5-O-benzoyl-1-O-methyl-2,3-dideoxyriboses 9b and 10b with silylated thymine in the presence of TiCl4 proceeded highly diastereoselectively (92% de) to give the corresponding β-nucleotide analogues in good yield. A remarkable neighboring group participation of the methylenephosphonothioate functionality was observed in the course of the β-N-glycosylation.

The Myers-Saito-type cyclizations of enediyne derivatives via γ-oxo ketene acetal intermediates generated by the neighboring group participation of naphthoate ester groups in acidic media are described.

Reaction of 1-trimethylsilyl-2,2-difluorocyclopropane derivative with aldehydes in the presence of a catalytic amount of TBAF (4 mol%) provides the corresponding cyclopropylcarbinols via cleavage of the carbon-silicon bond.

Synthesis of a 1,10-diphenanthryl all- trans fused perhydrophenanthrene derivative and a recognition study in an aqueous media were carried out. A water-soluble derivative recognized certain benzene derivatives with 10 4 –10 5 M −1 of binding constant.

The acyclic enediyne possessing an aminomethyl group was designed and synthesized as a potential substrate for pyridoxal-dependent enzymes. Compound 2 was shown to give cycloaromatized products by the reaction with pyridoxal or isonicotinaldehyde via the toluene biradical intermediate.

Diethyl α-methoxy-α-alkynylmalotate derivatives of cis -enediynes were synthesized and they produced toluenebiradicals via the reaction cascade triggered by ester hydrolysis. Deuterium labeling studies suggested that the reaction involved the self quenching process by fairly fast disproportionation of toluene biradicals producing zwitterionic species.

A convergent synthesis provided a C 25 and a C 35 oxidopolyprene in which a farnesyl C 15 unit is connected in a head-to-head fashion to a geranyl C 10 or a geranylgeranyl C 20 unit. When incubated with recombinant β-amyrin synthase from Pisum sativum the C 25 oxidopolyprene was enzymatically converted to an unnatural novel tetracyclic sesterterpene, while the C 35 analogue did not afford any cyclization product.

Cis -enediyne derivatives 1 underwent Myers-type Cycloaromatization under acidic conditions via the enyne-allene intermediate 2 by the triggering action of the hydroxy group. Compound 1 showed pH dependent DNA-cleaving activity.

Novel 2-pyrone synthesis via the nucleophilic addition of active methine compounds to 2-alkynone has been developed. The reaction of active methine compounds with 2-alkynone provided 2-pyrones in good yields.

An alternative method for the preparation of MAC reagents, H-C(CN) 2 O-R, was developed. Using the proposed method, MAC reagents with acyl moiety were synthesized from malononitrile in more than 60% overall yields in three steps.

Regio- and stereoselective formation of the functionalized gem-difluorocyclopropane derivative was achieved through the Michael addition of lithium enolate of ester or amide with 4-bromo-4,4-difluorocrotonate 1 followed by the triethylborane-O 2 mediated intramolecular substitution reaction.

Development of enediyne model compounds possessing a cyanohydrin moiety is described. These model compounds generate enyne–allenylketones efficiently under mild basic conditions and the resulting biradicals showed potent DNA cleaving abilities.

Three optically active adamantane derivatives have been constructed starting from meso 7-methylidenebicyclo[3.3.1]nonan-3-one by employing two chirality induction processes, asymmetric aldolization and Sharpless asymmetric epoxidation.

Reactions of the cross-conjugated dienolate of 3-substituted 2-cyclohexenone 1b and 1c , 2-cyclohexenone ( 1d ), and 2,3-disubstituted 2-cyclohexenone 1e with methyl (S)-3-(2,2-dimethyl-1,3-dioxolan-4-yl)-2-propenate ( Z )- 2 gave highly diastereoselectively 3b, 3c, 3d and 3e , respectively. The presence of a methyl group at C-6 on cyclohexenone ring caused the stereoselectivity to change completely, so that the reaction of the lithium enolate of 9 with ( Z )- 2 and with ( E )-2 gave predominantly 11 and 12 , respectively.

Highly stereocontrolled synthesis of marine sesquiterpene upial was achieved from D -mannitol via fragmentation reaction of tricyclic compound 10 and samarium(II) iodide-induced cyclization of diformate 2.

A complex of perseitol (d-glycero-d-galacto-heptitol) and K+ ions in a molar ratio of 20:1 was isolated from the leaves of Scurrula fusca (Loranthaceae). The stereochemical structure of the complex was determined using several kinds of NMR techniques.

Core intermediates for the synthesis of anti-cancer agents, inhibitors of aminopeptidases and HIV proteases, 3-amino-2-hydroxy-4-phenylbutanoates were synthesized by using H-C(CN) 2 O-SiR 3 as a key reagent.

Iodolactonization of symmetrical diene-carboxylic imides (3a,b), derived from a camphorsultam, afforded chiral lactones (5) and (6) possessing aromatic substituents on quaternary carbons in high enantioselectivity with moderate diastereoselectivity.

Novel interleukin-1 inhibitors, triptoquinone A (1) and B(2), have been isolated from Tripterygium wilfordii v a r regelli, and their structures were elucidated mainly by spectroscopic methods including X-ray.

Total synthesis of (−)-mintlactone and (+)-isomintlactone has been achieved diastereoselectively via a fused butenolide construction strategy based on an intramolecular [3+2] cycloaddition reaction of nitrile oxide.

Synthesis of the sulfone containing 10-membered enediyne derivative 3 and its cycloaromatization in basic conditions via an allenic sulfone intermediate as well as its DNA cleaving activities are described.

Synthesis of the 10-membered heterocyclic enediyne 4 and its conversion to the benzenoid adduct 10 via the Bergman reaction are described.

The reaction of (S)-α-dibenzylamino aldehydes with dichloroisopropoxytitanium ester homoenolates gave the corresponding γ-aminoalkyl γ-lactones with high erythro selectivity. The same reaction by the use of amide homoenolates also afforded the corresponding 2-amino alcohols with high erythro-selectivity.

Synthesis of various nitrated oligo-N-methylpyrrolecarboxamide derivatives and their DNA cleaving activities under UV-A irradiation were described.