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In a survey of nonpeptide noncovalent inhibitors of the human 20S proteasome, we found that a novel tamoxifen derivative, RID-F (compound 6), inhibits all three protease activities of the proteasome at submicromolar levels. Structure-activity relationship studies revealed that a RID-F analog (RID-F-S*4, compound 25) is the smallest derivative compound capable of inhibiting proteasome activity, with a potency similar to that of RID-F. Kinetic analyses of the inhibition mode and competition experiments involving biotin-belactosin A (a proteasome inhibitor) binding indicated that the RID-F derivatives interact with the protease subunits in a different manner. Culturing of human cells with these compounds resulted in accumulation of ubiquitinated proteins and induction of apoptosis. Thus, the RID-F derivatives may be useful lead chemicals for the generation of a new class of proteasome inhibitors.

Tamoxifen is an anticancer agent widely used for treatment of estrogen receptor (ERα)-positive breast cancer. We previously developed a novel synthesis of tamoxifen and its derivatives, named Ridaifens (RIDs). Some of them, including RID-SB8, exhibited a stronger anticancer activity than tamoxifen in ERα-positive MCF-7 cells while having lost the affinity for ERα, suggesting an ERα-independent anticancer mode of action. In this study, we investigated the underlying mechanism by which RID-SB8 exerts anticancer activity. As expected, anticancer activity of RID-SB8 was not influenced upon knockdown of ERα expression in MCF-7 cells. RID-SB8 exerted similar anticancer effects on thirteen ERα-negative cancer cell lines including human gliosarcoma SF539 cells. In SF539 cells, RID-SB8 triggered loss of mitochondrial membrane potential (ΔΨ(m)) and progression of apoptosis accompanied by activation of caspases and translocation of apoptosis-inducing factor (AIF) to the nucleus. Furthermore, it induced reactive oxygen species (ROS), and a ROS scavenger, N-acetylcysteine (NAC), canceled loss of ΔΨ(m) and progression of apoptosis triggered by RID-SB8. Using fifteen human cancer cell lines, we demonstrated a significant correlation between RID-SB8 concentration required for ROS production and that required for cytotoxic effect across these cell lines, but such correlation was not observed for tamoxifen. Finally, the selective induction of ROS and cytotoxic effect on cancer cells by RID-SB8 were confirmed. From these results, we concluded that RID-SB8 exerts an anticancer effect via a mode of action distinct from tamoxifen, and that RID-SB8 could become a promising anticancer lead compound which selectively induces ROS formation and apoptosis in cancer cells.

Autophagy is a self-proteolysis process in eukaryotic cells that results in the sequestering of intracellular proteins and organelles in autophagosomes. Activation of autophagy progress continued growth of some tumors, instead extensive autophagy induces cell death. In a previous study, we synthesized a novel tamoxifen derivative, Ridaifen (RID)-B. RID-B induced mitochondria-involved apoptosis even in estrogen receptor (ER)-negative cells. Since tamoxifen induces autophagy other than apoptosis, we treated ER-negative Jurkat cells with RID-B in the present study. RID-B treatment induced apoptosis and LC3 and lysosome colocalization, which results in the formation of autolysosomes. Western blotting revealed that LC3 was converted to LC3-I to LC3-II with RID-B treatment, suggesting that RID-B induced autophagy without ER involvement. Moreover, overexpression of the anti-apoptotic protein Bcl-2 suppressed the RID-B-induced cell death, but not the induction of autophagy. These results presumed that RID-B-induced autophagy is independent of Bcl-2, making RID-B-induced autophagy different from RID-B-induced apoptosis. Since Beclin 1 level is unchanged during RID-B treatment, RID-B induced autophagy pathway is Bcl-2/Beclin1 independent noncanonical pathway.

The anti-tumor agent, tamoxifen, is easily synthesized by the successive allylation of benzaldehyde and the Friedel–Crafts alkylation reaction of anisole with the intermediary homoallyl silyl ethers, followed by the migration of the double bond to form the desired tetra-substituted ethylenes. Several derivatives of tamoxifen are also produced according to a similar synthetic strategy.

Of the 16 possible modes of the oxidation-6π-electrocylization-Diels–Alder reaction cascade for an epoxyquinone, and eight for a 2-alkenyl-3-hydroxymethyl-2-cyclohexen-1-one, only the endo - anti (epoxide) -anti (Me)-hetero and endo - anti (Me)-hetero are respectively observed, while both the endo - anti (epoxide) -anti (Me)-hetero and exo - anti (epoxide) -anti (Me)-homo reaction modes occur with epoxy-4-hydroxycyclohexenones owing to a hydrogen-bonding interaction.

An effective method for the total synthesis of 1 (AMF-26), a potentially promising new anticancer drug that disrupts the Golgi system by inhibiting the ADP-ribosylation factor 1 (Arf1) activation, has been developed for the first time. The construction of the chiral linear precursor (a key to the synthesis) was achieved by the asymmetric aldol reaction followed by the computer-assisted predictive stereoselective intramolecular Diels–Alder reaction. The global antitumor activity of the totally synthetic 1 against a variety of human cancer cells was assessed using a panel of 39 human cancer cell lines (JFCR39), and it was shown that the synthetic 1 strongly inhibited the growth of several cancer cell lines at concentrations of less than 0.04 μM. Biological assays of novel derivatives, 26 and 31, which have different side-chains at the C-4 positions in the Δ1,2-octalin backbone, disclosed the importance of the suitable structure of the side-chain containing conjugated multidouble bonds.

Various β-lactones were prepared from β-hydroxycarboxylic acids by intramolecular dehydration condensation using MNBA, an effective coupling reagent, along with a nucleophilic catalyst. The transition state that provides the desired 4-membered ring model system is disclosed by density functional theory (DFT) calculations, and the structural features of the transition form are discussed. This method was successfully applied to the asymmetric total synthesis of tetrahydrolipstatin (THL), an antiobestic drug used in clinical treatment to inhibit the activity of pancreatic lipase.

An efficient method for the synthesis of macrolides directly from ω-hydroxycarboxylic acids is established by using 4-(trifluoromethyl)benzoic anhydride and a catalytic amount of active titanium(IV) salts together with chlorotrimethylsilane under mild conditions.

Various carboxylic esters are prepared in excellent yields from nearly equimolar amounts of free carboxylic acids and alcohols at room temperature by combined use of 4-(trifluoromethyl)benzoic anhydride and a catalytic amount of active titanium(IV) salt together with chlorotrimethylsilane.

In the presence of a catalytic amount of active titanium(IV) salt generated in situ from 1 mol of TiCl4 and 2 mol of AgOTf, weakly nucleophilic anilines react under mild conditions with nearly equimolar amounts of silyl carboxylates to afford the corresponding anilides in excellent yields using 4-(trifluoromethyl)benzoic anhydride. The mixed anhydride formed in situ from trimethylsily acetate and 4-(trifluoxomethyl)benzoic anhydride, a key intermediate of this reaction, was detected by 1H NMR experiment. Further, it was shown that the reaction of the mixed anhydrides and 2-nitroaniline was faster than that of the corresponding homo anhydrides and 2-nitroaniline.

(R)-(+)-N-Methylbenzoguanidine ((R)-NMBG) was found to function as an efficient acyl-transfer catalyst for the kinetic resolution of racemic secondary benzylic alcohols in the presence of achiral carboxylic acids and pivalic anhydride. The use of a tertiary amine in this reaction is not necessary to attain good chemical yields of the products. It was determined that diphenylacetic acid could be employed as the most suitable acyl donor for achieving a high enantioselectivity for the kinetic resolution of the racemic secondary benzylic alcohols having normal aliphatic alkyl chains at the C-1 positions. On the other hand, a less-hindered carboxylic acid, such as 3-phenylpropanoic acid, functioned as a better acyl donor for the kinetic resolution of racemic secondary benzylic alcohols having branched aliphatic alkyl chains at the C-1 positions.

The kinetic resolution of racemic alcohols (I) with phenylpropanoic acid (II) is examined and the optimized structure of the oxazole part in substrates (I) is determined.

The first efficient non-enzymatic method for providing optically active 1-heteroarylalkanol derivatives by kinetic resolution is given.

A widely applicable method is developed via generation of mixed anhydrides followed by reaction with bis(9-phenanthryl)methanol in the presence of (+)-benzotetramisole as the catalyst.

In the presence of a catalytic amount of Lewis acid, various carboxylic esters or S-phenyl carbothioates are prepared in excellent yields by the respective reactions of equimolar amounts of silyl carboxylates and alkyl silyl ethers or phenyl silyl sulfides with 4-trifluoromethylbenzoic anhydride.

The lactonization of silyl ω-siloxycarboxylates is successfully carried out under mild conditions in good to high yields by using p-trifluoromethylbenzoic anhydride and a catalytic amount of active acidic species generated in situ from TiCl4 and AgClO4.

Highly diastereo- and enantioselective aldol-type reactions of a silyl enol ether with aldehydes including aromatic, aliphatic, and α,β-unsaturated ones are performed in propionitrile (solvent) by the use of a catalytic amount of chiral tin(II) Lewis acid consisting of tin(II) triflate and a chiral diamine. The asymmetric environments created by the chiral catalysts in the enantioselective aldol reaction are discussed by employing five kinds of chiral diamines.

Anti-α,β-dihydroxy thioesters are prepared with excellent enantioselectivities by the asymmetric aldol reaction between both achiral aldehydes and silyl enol ethers derived from α-benzyloxy thioesters in the presence of a chiral promoter consisted of chiral diamine coordinated tin(II) triflate and dibutyltindiacetate.

In the presence of a chiral promoter consisting of tin(II) triflate, a chiral diamine, and tributylin fluoride, the silyl enol ether of S-ethyl ethanethioate or S-tert-butyl ethanetioate reacts with aldehydes to afford the corresponding aldol-type adducts in good yields with high enantioselectivities. In the reaction of silyl enol ether of S-ethyl propanethioate with aldehydes, perfect stereochemical control is attained by the combined use of tin(II) triflate, a chiral diamine, and dibutylin diacetate. A wide variety of aldehydes, including aliphatic, α,β-unsaturated, and aromatic aldehydes, are applicable to this reaction. The chiral promoters are characterized by 119 Sn NMR spectra and proved to form the three-component complexes, which behave as chiral Lewis acids. The reaction proceeds directly from silyl enol ethers without any accompanying metal exchange on the enolates

Three types of sugars, 6-deoxy-L-tallose,4-C-methyl-D-ribose, and D-ribose were synthesized from both achiral starting materials, α,β-unsaturated aldehydes and silyl enol ethers of α-benzyloxy thioesters, by successive asymmetric aldol and vicinal dihydroxylation reactions.

syn-α,β-Dihydroxy thioesters are prepared in good yields with high diastereo- and enantioselectivities by the asymmetric aldol reaction of 1-trimethylsiloxy-1-ethylthio-2-t-butyldimethylsiloxyethene with aldehydes using a chiral promoter consisting of tin(II) triflate, a chiral diamine and dibutyltin diacetate.

Various carboxylic esters are prepared in good to excellent yields by the reaction of equimolar amounts of silyl derivatives of carboxylic acids and alcohols by using a catalytic amount of active Lewis acid in hexamethyldisiloxane, a solvent.

The α-hydroxy-α-methyl-β-hydroxy units are enantioselectively prepared by way of asymmetric aldol reactions between both achiral β,β- disubstituted silyl enolates and aldehydes. (-)-2-C-Methyl-D-threono-1,4-lactone is conveniently synthesized by using this reaction

In the presence of a catalytic amount of Lewis acid, various carboxylic esters or S-phenyl carbothioates are prepared in excellent yields by the respective reactions of equimolar amounts of silyl carboxylates and alkyl silyl ethers or phenyl silyl sulfides with 4-trifluoromethylbenzoic anhydride.

Highly diastereo- and enantioselective aldol-type reactions of a silyl enol ether with aldehydes including aromatic, aliphatic, and α,β-unsaturated ones are performed in propionitrile (solvent) by the use of a catalytic amount of chiral tin(II) Lewis acid consisting of tin(II) triflate and a chiral diamine. The asymmetric environments created by the chiral catalysts in the enantioselective aldol reaction are discussed by employing five kinds of chiral diamines.

In the presence of a catalytic amount of titanium(IV) salt, various S-phenyl carbothioates are prepared in excellent yields by the reaction of nearly equimolar amounts of silyl derivatives of carboxylic acids and benzenethiols with p-trifluoromethylbenzoic anhydride.

An efficient method for the synthesis of macrolides directly from ω-hydroxycarboxylic acids is established by using 4-(trifluoromethyl)benzoic anhydride and a catalytic amount of active titanium(IV) salts together with chlorotrimethylsilane under mild conditions.

Various carboxylic esters are prepared in excellent yields from nearly equimolar amounts of free carboxylic acids and alcohols at room temperature by combined use of 4-(trifluoromethyl)benzoic anhydride and a catalytic amount of active titanium(IV) salt together with chlorotrimethylsilane.

In the presence of a catalytic amount of active titanium(IV) salt generated in situ from 1 mol of TiCl4 and 2 mol of AgOTf, weakly nucleophilic anilines react under mild conditions with nearly equimolar amounts of silyl carboxylates to afford the corresponding anilides in excellent yields using 4-(trifluoromethyl)benzoic anhydride. The mixed anhydride formed in situ from trimethylsily acetate and 4-(trifluoxomethyl)benzoic anhydride, a key intermediate of this reaction, was detected by 1H NMR experiment. Further, it was shown that the reaction of the mixed anhydrides and 2-nitroaniline was faster than that of the corresponding homo anhydrides and 2-nitroaniline.

syn- and anti-1,2-Diol units were prepared by using asymmetric aldol reactions of the silyl enol ethers derived from α-alkoxythioacetic S-esters with aldehydes. In the presence of tin(II) triflate, a chiral diamine, and dibutyltin diacetate, (Z)-2-benzyloxy-1-ethylthino-1-(trimethylsiloxy)ethene reacted with aldehydes to afford the corresponding anti-aldol adducts in high yields with excellent diastereo- and enantioselectivities, while syn-adducts were obtained from (Z)-2-(t-butyldimethylsiloxy)-1-ethylthio-1-(trimethylsiloxy)ethene and aldehydes under the same reaction conditions. Thus, both diastereomers can be synthesized in excellent enantiomeric excesses by simply choosing the protective groups of the alkoxyl parts of the silyl enol ethers.

Catalytic Diels-Alder reactions between several 1,3-dienes and α,β-unsaturated ketones are effectively promoted by the combined use of diphenyltin sulfide (Ph2Sn=S) and silver perchlorate or Lawesson’s reagent (2,4-bis(4-methoxyphenyl)-1,3-dithia-2,4-diphosphetane-2,4-disulfide) and silver perchlorate under mild conditions.

1-t-Butyldimethylsiloxy-8,11,11-trimethylbicyclo[5.3.1]undec-7-en-9-one (2) has been synthesized via intramolecular aldol condensation of the precursor 3 by combined use of lithium diisopropylamide (LDA) and CeCl3. The dicarbonyl compound 3 was prepared by allylation of 8-membered ring ketone 6b.

Optically active 3,7-dibenzyloxy-4,8-di-t-butyldimethylsiloxy-5,5-dimethyl-6-p-methoxybenzyloxy-2-octanone (2) has been synthesized by way of diastereoselective aldol reaction between 4-benzyloxy-5-t-butyldimethylsiloxy-2,2-dimethyl-3-p-methoxy-benzyloxypentanal (3) and ketene silyl acetal 4 using MgBr2·OEt2 as a catalyst. The chiral pentanal 3 was synthesized either by asymmetric aldol reaction of both prochiral aldehyde 5 and ketene silyl acetal 4 using a chiral Lewis acid or by diastereoselective aldol reaction between the chiral aldehyde 6 derived from L-serine and the lithium enolate derived from methyl isobutyrate.

Optically active 7-t-butyldimethylsiloxy-4,8-dibenzyloxy-6,6-dimethyl-5-p-methoxybenzyloxy-2-cycloocten-1-one (1) was synthesized from 3,7-dibenzyloxy-4,8-di-t-butyldimethylsiloxy-5,5-dimethyl-6-p-methoxybenzyloxy-2-octanone (2) by way of intramolecular Reformatsky-type reaction using SmI2.

Various carboxylic esters are prepared in good to high yields from equimolar amounts of free carboxylic acids and alcohols by the combined use of octamethylcyclotetrasiloxane and a catalytic amount of TiCl(OTf)3.

Optically active 9-t-butyldiphenylsiloxy-11,11-dimethyl-5-methoxymethoxy-1,2,6-tribenzyloxybicyclo[5.3.1]undec-3,7-diene (12) was synthesized from diketone 9 via an intramolecular aldol reaction. The diketone 9 was synthesized from 7-t-butyldimethylsiloxy-4,8-dibenzyloxy-6,6-dimethyl-5-p-methoxy-benzyloxy-2-cycloocten-1-one (1) by way of a two-step sequence using diastereoselective allylation with allylmagnesium bromide followed by Wacker oxidation.

Optically active novel taxoids were efficiently synthesized from 8-membered ring compound 3 by successive constructions of BC and ABC ring systems via each intramolecular aldol and intramolecular pinacol coupling reactions.

Optically active 2α,10β-dibenzyloxy-11β-(t-butyldimethylsiloxy)-7β-hydroxy-1α-(4-methoxybenzyloxy)–8β,15,15-trimethyl-4-methylene-trans-bicyclo[6.4.0]dodecan-9-one 2 that corresponds to BC ring system of Taxol was prepared from 8-membered ring enone 3 in high yield via stereoselctive Michael addition and successive intramolecular aldol cyclization. The above 8-membered ring enone 3 was synthesized from the linear optically active polyoxy-compound 4 by SmI2-mediated intramolecular aldol cyclization.

Total asymmetric synthesis of Taxol was completed by dehydration condensation between a protected N-benzoylphenylisoserine 4 or 9 and 7-TES baccatin III which was prepared from 8-membered ring enone. Taxol side chains 4, 7, 9 and 11, optically active protected N-benzoylphenylisoserines, were successfully synthesized by enantioselective aldol reaction from two achiral starting materials, benzaldehyde and an enol silyl ether derived from S-ethyl benzyloxyethanethioate.

Baccatin III was efficiently synthesized from the BC ring system of Taxol,2α,10β-dibenzyloxy-11β-(t-butyldimethylsil-oxy)-7β-hydroxy-1α-(4-methoxybenzyloxy)-8β,15,15-trimethyl-4-methylene-trans-bic...

An efficient method for the synthesis of (−)-cephalosporolide D was established via successive enantioselective aldol reaction and effective construction of 8-membered ring lactone moiety.

Various carboxylic esters were obtained in high yields from free carboxylic acids and several alcohols including bulky ones by using O,O′-di(2-pyridyl) thiocarbonate and a catalytic amount of DMAP.