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The stereo-controlled total synthesis of (−)-domoic acid is described, including the crucial formation of the trisubstituted Z-olefin moiety and the incorporation of the side chain using modified Julia–Kocieński reaction in the final stage.

The first total synthesis of (7″R,8″R)-, (7″S,8″S)-isomers of princepin (1) and (7″R,8″R)-, (7″S,8″S)-isomers of isoprincepin (2) was accomplished in a highly stereoselective manner via para quinomethide-mediated construction of the furofuran and 1,4-benzodioxane rings. Structural confirmation methods of 1 and 2 were established by CD and HPLC analysis of each diastereomers with natural products.

Hypertrophy and hyperplasia of white adipocytes induce obesity, leading to diseases such as type 2 diabetes and hypertension, and even cancer. Hypertrophy of white adipocytes is attributed to the excessive storage of the energy form of triglycerides in lipid droplets (LDs). LDs are fat storage organelles that maintain whole-body energy homeostasis. It is important to understand the mechanism of LD formation for the development of obesity therapy; however, the regulatory mechanisms of LD size and formation are not fully understood. In this study, we demonstrated that the PPM family phosphatase PPM1D regulates LD formation. PPM1D specific inhibitor, SL-176 significantly decreased LD formation via two different pathways: dependent of and independent of adipocyte-differentiation processes. In the mature white adipocytes after differentiation, LD formation was found to be controlled by PPM1D via dephosphorylation of Ser511 of perilipin 1. We found that inhibition of PPM1D in mature white adipocytes significantly reduced the size of the LDs via dephosphorylation of Ser511 of perilipin 1 but did not change the lipolysis sensitivity and the total amount of lipid in cells. Collectively, the results of this study provide evidence that PPM1D plays an important role in LD formation in mature adipocytes.

Sophoraflavanone H (1) is a polyphenol with a hybrid-type structure containing 2,3-diaryl-2,3-dihydrobenzofuran and flavanone ring moieties. This compound and related analogues are promising leads for antimicrobial and antitumor drug development. Here we describe a total synthesis of 1 and its diastereomer. The dihydrobenzofuran and flavanone rings were constructed by a Rh-catalyzed asymmetric C-H insertion reaction and selective oxy-Michael reaction. The absolute configuration of 1 was established by X-ray crystallographic analysis and CD spectral investigation of synthetic derivatives.

A formal total synthesis of pactamycin (1) has been accomplished by face-selective and regioselective nitroso Diels–Alder (NDA) reaction of acyl nitroso compound 14, which contains a camphorsultam ...

Supporting information for this article is available online at https://doi.org/10.1055/s-0036-1588424., Upon treatment with triisopropylsilyl trifluoromethanesulfonate and 2,2,6,6-tetramethylpiperidine, alkanenitriles undergo direct addition to aldehydes under mild non-basic neutral conditions to provide triisopropylsilyl ethers of β-hydroxy nitriles in good yield. The reaction proceeds through generation of an N-silyl ketene imine intermediate in situ from the alkanenitrile followed by nucleophilic addition of the intermediate to the aldehyde.

The first total synthesis of (7″

The asymmetric total synthesis of laurallene was achieved in 13 steps for the longest linear sequence with 3.3% overall yield from commercially available trans-2-pentenal. This synthesis features the highly efficient construction of a branched ether system with five oxygenated asymmetric stereocenters by the combination of a palladium-catalyzed alkoxy substitution reaction and a cobalt-catalyzed Mukaiyama oxidative cyclization.

Andrastins are meroterpenes isolated from Penicillium sp. FO-3929 that display highly potent inhibitory activities toward protein farnesyltransferase. Structurally, they possess a unique steroidal tetracyclic skeleton (the ABCD-ring) with three contiguous quaternary stereocenters on the C-ring. Herein, we describe our nitrile cyclization-based approach to the stereoselective construction of the BCD-ring system of andrastins, which contains three contiguous quaternary stereocenters on the C-ring and the correct oxidation states of the D-ring.

Brasilicardins, bacterial diterpenoid natural products that display highly potent immunosuppressive activity, are promising immunosuppressant drug candidates. Structurally, they can be described as hybrids of terpenoids, amino acids, and saccharides, and share a characteristic highly strained anti‐syn‐anti‐fused perhydrophenanthrene terpenoid scaffold (ABC‐ring system) with two quaternary asymmetric carbon atoms. A unified and stereoselective total synthesis of all four brasilicardins has been designed based on the strategic use of an intramolecular conjugate addition. The ABC‐ring system was initially constructed with high stereocontrol by novel intramolecular conjugate additions of Weinreb amides and in situ generated (Z)‐vinyl copper species. The late‐stage common intermediate was subjected to stereoselective installation of the amino acid component, followed by introduction of the saccharide unit via glycosylation to accomplish the total synthesis of brasilicardins A–D. Our synthesis offers opportunities to synthesize various brasilicardin analogues for biological and pharmacological investigations.

Protein phosphatase Magnesium-dependent 1, Delta (PPM1D) is a wild-type p53-inducible Ser/Thr phosphatase that acts as a negative regulator of the p53 tumor suppressor. Gene amplification and overexpression of PPM1D have been reported in various cancers including leukemia and neuroblastoma. Therefore, PPM1D is a promising target in cancer therapy. It has been reported that PPM1D knockout mice exhibit neutrophilia in blood and show a defective immune response. Here, we found that inhibition of PPM1D induced neutrophil differentiation of human promyelocytic leukemia cell line HL-60. The combination of a PPM1D inhibitor and all-trans retinoic acid significantly increased their differentiation efficiency. The PPM1D inhibitor also induced G1 arrest in HL-60 cells. Our results suggest that PPM1D may be a potential therapeutic target for blood cell diseases including leukemia.

PPM1D is a p53-inducible Ser/Thr phosphatase. One of the main functions of PPM1D in normal cells is to act as a negative regulator of the p53 tumor suppressor by dephosphorylating p53 and several kinases. PPM1D is considered an oncoprotein owing to both its functions and the fact that gene amplification and overexpression of PPM1D are reported in several tumors. Recently, PPM1D mutations resulting in C-terminal truncated alterations were found in brainstem gliomas and colorectal cancers, and these mutations enhanced the activity of PPM1D. Therefore, C-terminal truncated PPM1D should be also considered as a potential candidate target of anticancer drugs. Here we showed that combination treatment with PPM1D-specific inhibitor SPI-001 and doxorubicin suppressed cell viability of HCT-116 cells overexpressing C-terminal truncated PPM1D through p53 activation compared with doxorubicin alone. Our results suggest that combination treatment with PPM1D inhibitor and doxorubicin may be a potential anti-cancer treatment in PPM1D-mutated cancer cells.

In the presence of triethylsilyl trifluoromethanesulfonate and triethylamine, aliphatic nitriles undergo addition reactions with aldonitrones under non-basic, mild conditions, providing O-tri­ethylsilyl ethers of β-N-hydroxyamino nitriles with high yield. The reaction appears to proceed through formation of an N-silyl ketene imine in situ followed by a Mannich-type reaction.

This review provides a compilation of the most recent synthetic approaches and total syntheses of zoanthamine alkaloids, which are structurally unique heptacyclic marine natural products that display a range of interesting biological activities. This review is focused on synthetic methodologies for the construction of the three adjacent quaternary asymmetric carbon atoms on the cyclohexane ring (C-ring) of these compounds. The literature covered in this review dates from 2008 to the end of 2013.

An efficient synthetic method for 2-cyano-1,4-cycloheptadiene derivatives was developed on the basis of divinylcyclopropane rearrangement. The substrates were prepared from 2-vinylcyclopropanecarbonitrile and an α,β-epoxysilane through a Peterson olefination. The resulting 2-cyano-1,4-cycloheptadiene underwent deprotonation at the doubly allylic methylene group to afford a novel cycloheptadienyl anion, a useful intermediate for synthesizing polycyclic compounds.

The previously unexplored reactivity of N-silyl ketene imines in organic synthesis is reported. Benzyl nitriles containing an alkenyl or aryl group at the ortho position were smoothly converted into aryl amines in good yields under two sets of mild silylation conditions: (1) nonbasic conditions using TMSNTf2–iPr2NEt or (2) basic anionic conditions using lithium diisopropylamide–triisopropylsilyl chloride (LDA–TIPSCl). The reaction probably proceeds via in situ generation of an N-silyl ketene imine followed by 6π-electrocyclization and aromatization.

An efficient method for constructing carbocycles with all-carbon quaternary stereocenters has been developed on the basis of a stereoselective cyclization reaction of α,β-unsaturated lactones having an alkanenitrile side chain. Treatment of the substrate with lithium hexamethyldisilazide (LiHMDS) in the presence of triisopropylsilyl chloride (TIPSCl) led to the generation of the corresponding α-cyano carbanion species which readily underwent an intramolecular conjugate addition reaction. It was found that the combined use of trimethylsilyl trifluoromethanesulfonate (TMSOTf) and triethylamine is also effective for the cyclization reaction without using a strong base. Interestingly, different stereochemical outcomes were observed in the two cyclization methods.

A series of 4-cyanoazulene derivatives 1–5 were synthesized from 4-cyanohexahydroazulen-1-one, which was efficiently obtained by the annulation of the seven-membered ring on the cyclopentenone skel...

A novel stereoselective S N 2′ alkylation reaction sequence of the γ,δ-epoxy α,β-unsaturated ester system has been developed which involves a regioselective substitution reaction with chloride ions at the γ-position and a subsequent S N 2′ alkylation reaction of the resulting γ-chloro-δ-hydroxy derivatives with a R 3 Al–CuCN reagent. The new methodology was demonstrated to be applicable to a variety of substrates and to provide various δ-hydroxy-α-alkyl-β,γ-unsaturated esters including those bearing a quaternary asymmetric carbon atom at the α-position in a highly stereoselective manner and high yields.

The unprecedented, stereospecific interconversion of cis- and trans- γ,δ-epoxy α,β-unsaturated ester systems has been realized, which involves the palladium-catalyzed stereospecific alkoxy or hydroxy substitution reaction with double inversion of configuration at the γ-position as the key step. The new methodology is not only applicable to various disubstituted and trisubstituted epoxy unsaturated esters, but also these interconversions proceed with an extremely high degree of stereoselectivity and efficiency.

The stereospecific epoxide-opening reactions of 1,1-dibromo-3,4-epoxy-1-alkenes with allyltributylstannane and with ketene silyl acetals in the presence of a Lewis acid are described. Both the reactions occurred regioselectively at the allylic position via an S N 2 process giving rise to a single product, respectively. Treatment of the products by the latter reaction with p -TsOH afforded various 3,4- anti - and 3,4- syn -disubstituted γ-lactones in a highly stereoselective manner and high yields.

The previously unexplored reactivity of N-silyl ketene imines in organic synthesis is reported. Benzyl nitriles containing an alkenyl or aryl group at the ortho position were smoothly converted into aryl amines in good yields under two sets of mild silylation conditions: (1) nonbasic conditions using TMSNTf2–iPr2NEt or (2) basic anionic conditions using lithium diisopropylamide–triisopropylsilyl chloride (LDA–TIPSCl). The reaction probably proceeds via in situ generation of an N-silyl ketene imine followed by 6π-electrocyclization and aromatization.

Protein phosphatase magnesium-dependent 1δ (PPM1D, Wip1) is a p53 inducible serine/threonine phosphatase. PPM1D is a promising target protein in cancer therapy since overexpression, missense mutations, truncating mutations, and gene amplification of PPM1D are reported in many tumors, including breast cancer and neuroblastoma. Herein, we report that a specific inhibitor, SL-176 that can be readily synthesized in 10 steps, significantly inhibits proliferation of a breast cancer cell line overexpressing PPM1D and induces G2/M arrest and apoptosis. SL-176 decreases PPM1D enzyme activity potently and specifically in vitro. These results demonstrate that SL-176 could be a useful lead compound in the development of effective anti-cancer agents.

There is wide interest in the epothilones, which like the taxoids initiate cytotoxicity through microtubule stabilization. Briefly described is an application of a ring-closing metathesis reaction toward the synthesis of epothilones as carried out in our laboratory. This has led to the discovery of the (E)-9,10-dehydroepothilones as second-generation anticancer drug candidates.

The synthetic versatility of the addition products is further examined by the transformation of the cyano group in (XIa) into a carboxamide, a carboxylic acid or an aminomethyl functionality.

Without the stereodirecting ability of 2-substituents, strategies to prepare 2-deoxyglycosides selectively in high alpha- or beta-anomeric forms rely heavily on indirect sequences from glycals or latent 2-deoxysugars. As such, these require a subsequent reductive step that would be unsuitable for many complex natural products and for any viable total synthesis program. A case in point is that of the kedarcidin chromophore and its alpha-linked 2,6-dideoxysugars, L-mycarose and L-kedarosamine. In particular, direct and efficient alpha-selective methods for allo-configured systems are especially difficult to realise. Herein we describe a direct, potent, and mild protocol to efficiently generate alpha-L-mycarosides from thioglycosides by using AgPF6, which is exemplified by the alpha-mycosylation of an advanced kedarcidin substructure. Although the present method is applicable to other 2-deoxy systems, such as the synthesis of alpha-L-kedarosaminides, normal 2-oxythioglycosides remain inert to AgPF6 and can be used as acceptors armed with strategic anomeric linkages.

The ansamacrolide moiety of kedarcidin has been constructed with complete atropselectivity via intramolecular Sonogashira coupling.

Reaction of cyclopropane (I) with oxiranes in the presence of BuLi produces 2-cyano-1,4-cycloheptadienecarbonitriles after thermal rearrangement of the intermediates.

We developed a new method for stereoselective construction of an all-carbon quaternary stereogenic center on a carbocyclic ring based on regio- and stereoselective S(N)2' alkylation reactions of γ,δ-epoxy-α,β-unsaturated cyclic ketones. Treatment of the ketones, which were readily prepared in enantiomerically pure form by means of aldol condensations between 3-ethoxy-2-cycloalkenones and α,β-epoxy aldehydes, with a R(2)Zn-CuCN reagent afforded anti-S(N)2' products stereoselectively. Conversely, the corresponding syn-S(N)2' products were stereoselectively obtained through two-step transformations of the same γ,δ-epoxy-α,β-unsaturated cyclic ketones: (1) conversion of the epoxide moiety to a chlorohydrin by treatment with MgCl(2) and (2) subsequent S(N)2' substitution of the chlorohydrin with a R(2)Zn-CuCN reagent. These substitution products with their chiral trans-allylic alcohol moieties are promising precursors for complex molecules. For example, Eschenmoser-Claisen rearrangement of one of the substitution products resulted in stereoselective formation of a keto amide having contiguous quaternary and tertiary stereogenic centers.

The efficient methodology allows the construction of carbocycles with all-carbon quarternary stereocenters from α,β-unsaturated lactones having an alkanenitrile side chain.

Zoanthamine alkaloids, isolated from organisms in the Zoanthus genus, constitute a distinctive family of marine metabolites. These molecules exhibit a broad spectrum of unique biological properties. For example, norzoanthamine inhibits interleukin-6, the key mediator of bone resorption in osteoporosis, providing a promising drug candidate for a disease that affects more than 10 million people over age 50 in the United States. In addition, these natural products are characterized by a densely functionalized heptacyclic framework, as exemplified by the structures of zoanthamine, norzoanthamine, and zoanthenol, which makes them extremely attractive targets for chemical synthesis. Prior to our first total synthesis of norzoanthamine in 2004, the densely functionalized and complex stereostructures of the zoanthamine alkaloids had impeded synthetic studies of these molecules. In this Account, we describe our synthetic approach toward the total synthesis of zoanthamine alkaloids, focusing on how we overcame various synthetic challenges. At the beginning of our synthetic studies, we aimed to develop an efficient route that was flexible enough to provide access to several members of the family while allowing the synthesis of various analogues for biological testing. Our first project was the total synthesis of norzoanthamine, and we established an efficient synthetic route based on a novel strategy involving the following key features. First, we used a sequential three-component coupling reactions and subsequent photosensitized oxidation of a furan moiety to synthesize the precursor for the key intramolecular Diels-Alder reaction. Second, the key intramolecular Diels-Alder reaction constructed the ABC-ring carbon framework bearing two adjacent quaternary asymmetric carbon atoms at the C12 and C22 positions in a single stereoselective step. Third, we installed the third quaternary asymmetric carbon center at the C9 position by an intramolecular acylation of a keto alcohol followed by successive O-methylation and C-methylation reactions with complete stereoselectivity. Through the exploitation of a deuterium kinetic isoptope effect, we then efficiently synthesized the alkyne segment. Next, a coupling reaction between the alkyne segment and the amino alcohol segment and several subsequent synthetic transformations afforded the bis-aminoacetalization precursor. Finally, bis-aminoacetalization reactions carried out in one-pot constructed the DEFG-ring system and culminated in the total synthesis of norzoanthamine. Our synthetic route to norzoanthamine also allowed access to other zoanthamine alkaloids from a common synthetic intermediate, by way of stereoselective introduction of the C19 methyl group for zoanthamine, and isoaromatization for construction of the aromatic A-ring in zoanthenol. The chemistry described here not only allowed us to overcome formidable synthetic challenges but also opened a completely chemical avenue to naturally occurring zoanthamine alkaloids and their synthetic derivatives.

Pink-pigmented facultatively methylotrophic bacteria (PPFMs) were isolated from fourteen kinds of phylloplanes in Pinus densiflora forest. PPFMs were Gram-negative, lophotrichously flagellated rods and attacked glucose fermentatively. All pink isolates utilized methanol, methylamine and formic acid as the sole carbon source but did not utilize methane. The PPFMs belonged to the genus Methylobacterium. The methylobacteria were found on the every phylloplane of the plants in P. densiflora forest. The fluctuation pattern in population of Methylobacterium was summerized as follows : (1) On the living leaves of Pinus densiflora, Methylobacterium occurred abundantly during summer although the number decreased abruptly in winter. The airborne methylobacteria behaved in the similar way as on the pine phylloplane. (2) On the phylloplanes of Cryptomeria japonica, Juniperus rigida and Ilex pedunculosa, these bacteria occurred even in winter. (3) Methylobacterium disappeared during the period from November to January on the leaves of Chamaecyparis obtusa and Eurya japonica. (4) Through the year round, higher occurrence of Methylobacterium was observed on the each phylloplane of the deciduous trees (Rhododendron macrosepalum, R. reticulatum, Lyonia elliptica, Quercus serrata, Rhus sylvestris, Vaccinium hirtum and Evodiopanax innovans) . These results indicate that Methylobacterium may reside favorably on the leaves of such plants as if it was epiphytic.

PPM1D is a p53-inducible Ser/Thr protein phosphatase. PPM1D gene amplification and overexpression have been reported in a variety of human tumors, including breast cancer and neuroblastoma. Because the phosphatase activity of PPM1D is essential for its oncogenic role, PPM1D inhibitors should be viable anti-cancer agents. In our current study, we showed that SPI-001 was a potent and specific PPM1D inhibitor. SPI-001 inhibited PPM1D phosphatase activity in PPM1D-overexpressing human breast cancer cells and increased phosphorylation of p53. Furthermore, SPI-001 suppressed cell proliferation by inducing apoptosis. Our present study suggested that SPI-001 was a potential lead compound in developing anti-cancer drugs.

The total synthesis of zoanthenol, a unique aromatic member of the zoanthamine alkaloids, which has exhibited potent anti-platelet activities on human platelet aggregation, is described in full detail. The key step involves a Bronsted acid-promoted isoaromatization in the AB ring system to install the crucial aromatic ring. We have not only succeeded in the first total synthesis of zoanthenol, but also established an alternative efficient synthetic route from the commercially available norzoanthamine hydrochloride to zoanthenol.

The total synthesis of zoanthenol, a unique aromatic member of the zoanthamine alkaloids, which has exhibited potent anti-platelet activities on human platelet aggregation, is described in full detail. The key step involves a Bronsted acid-promoted isoaromatization in the AB ring system to install the crucial aromatic ring. We have not only succeeded in the first total synthesis of zoanthenol, but also established an alternative efficient synthetic route from the commercially available norzoanthamine hydrochloride to zoanthenol.

A novel stereoselective S N 2′ alkylation reaction sequence of the γ,δ-epoxy α,β-unsaturated ester system has been developed which involves a regioselective substitution reaction with chloride ions at the γ-position and a subsequent S N 2′ alkylation reaction of the resulting γ-chloro-δ-hydroxy derivatives with a R 3 Al–CuCN reagent. The new methodology was demonstrated to be applicable to a variety of substrates and to provide various δ-hydroxy-α-alkyl-β,γ-unsaturated esters including those bearing a quaternary asymmetric carbon atom at the α-position in a highly stereoselective manner and high yields.

The stereospecific epoxide-opening reactions of 1,1-dibromo-3,4-epoxy-1-alkenes with allyltributylstannane and with ketene silyl acetals in the presence of a Lewis acid are described. Both the reactions occurred regioselectively at the allylic position via an S N 2 process giving rise to a single product, respectively. Treatment of the products by the latter reaction with p -TsOH afforded various 3,4- anti - and 3,4- syn -disubstituted γ-lactones in a highly stereoselective manner and high yields.